The Brotherhood of Steel "Ad Victorium" quest depicts Vault Boy standing in front of a giant robot foot. This is strongly suggesting the return of Liberty Prime, and if this is true than all but confirms that the Brotherhood of Steel in game is the same we saw in 3. That would in turn, confirm that the game truly does not take place 200 years after the war, meaning it isn't set in the same year as Fallout 3. In order for it to be set in 2277, one of 2 things would have to be the case

1. The Brotherhood of Steel manages to somehow fix Liberty Prime and become strong enough to maintain a presence in both D.C and Boston, possibly creating an empire or nation of sorts right after Fallout 3 ends.
2. There is more than one type of Liberty Prime type robot.

Both options don't make sense both logically and going along with the lore. I have said before that the Brotherhood of Steel is in no position by the end of Fallout 3 to be in the in the position the Brotherhood in 4 appears to be in. They have a few vertibirds, not the fleets that the chapter in 4 seem to possess. The Capital Wasteland is not a solved issue by any means at the end of 3. Yes they may have clean water, but the Wasteland still has multiple raider groups. Paradise Falls is still a massive slaver hub. Remaining mutants may not be a long term problem, but clearing them out in the weeks and months after Fallout 3 will still be a priority. Not to mention the civil war with the Outcasts and the fact that the Capital Wasteland is still a hellhole for the most part, with a few towns spread around the region whose only real cooperation with each other seems to just be trading. The Brotherhood has no reason to just send troops and equipment to Bostom for no logical reason when they have only started to fix the issues in their surrounding region. Liberty Prime is also destroyed and if they somehow manage to fix him, it wouldn't be in 2277. It took 20 years to fix him and he wasn't even fully completed at the end of Fallout 3. So if they do manage to repair him it would take more than a couple of months.The other option wouldn't make any sense either. Liberty Prime was never even finished before the war, why would they make multiple of the project they never bothered to complete in the first place.

Thus the only way he could be in the game and it not have it so the Brotherhood of Steel manage to fix a massive pre war project in weeks and then decide to randomly go to Boston, or that there are multiple Liberty Primes on the East Coast waiting at any second to strike, is that the Brotherhood after years manage to repair Liberty Prime. They could say that it was after the Brotherhood created a new nation out of the ruins of the Capital Wasteland, and somehow managed to gain massive industrial might, allowing them to build new vertibirds, weapons, and perhaps new power armor, equiping and growing their army to go along with the land they gain. The only way that any of this would be possible is if years go by, allowing the Brotherhood time to expand. The airship bearing the name of King Arthur's horse, the East Coast Brotherhood having Arthur Maxson, the presence of vertibirds when the Lyons BOS is the only known BOS with them. Now with the foot of what appears to be Liberty Prime, it is increasingly likely that this is the same group from 3. Some have said that it's possible they do something similar to Fable and they do a large timeskip but that doesn't seem like something Bethesda would do.

Todd Howard says at E3 "You then emerge 200 years later as the sole survivor of vault 111."

Do the math. Bombs drop in 2077. Emerge 200 years later. It's 2277 in Fallout 4 my friend.

Yeah but some are thinking he was not saying a LITERAL 200 years

I do think this takes place some time aftet 3 as the only brotherhood group to have vertibirds was Lyon's.

There is definetly a great chance that a new one is made. Or it could also be a whole different machine. We are dealing with such a technologically advanced place in Boston. Don't overthink the 200 years. And also, if youre saying it isn't exactly 200 because liberty prime is there, then youre saying it somehow moves from DC to Boston in a certain time period. Which in turn says that it could very well be fixed up and then moved to the Boston area. Don't think about the 200 years too much

Either way, if it isn't exactly 2277 it's pretty darn close. Close enough to technically be 2277.

He also said in videos for Fallout 3 that nobody ever enters of leaves Vault 101...

It's also become increasingly clear you probably aren't the sole survivor of Vault 111 either.

Or maybe it's not a foot, let alone Liberty Prime's. This isn't very damning evidence.

Two totally different things. One is a MAJOR story twist. The other is what year the game takes place.

Again. A story twist that you find out later.

It looks very much like a foot. Also there is previous concept art of a more militaristic, grey colored Liberty Prime that wasn't used from Fallout 3.

http://vignette3.wikia.nocookie.net/fallout/images/4/4d/LibertyPrime.png/revision/latest?cb=20110731212245

http://imgur.com/xDITpY5

They even look similar. Don't forget it they updated appearances for creatures and robot. To have it related to the Brotherhood quests make help the idea it's him rebuilt in some way.

I've heard of a magical location in Boston, where robots slaves serve their masters. They call it the Institute. It's also the very same place Robert House, CEO of RobCo, the company behind Liberty Prime, attended during his Pre-War years. Could it be that, the Brotherhood of Steel is going on a magical crusade to search for parts?

That doesn't look *anything* like Liberty Prime's foot, or a foot in general. If that's what they're going for, they're doing so poorly.

Well, we don't really know how much of a presence the BoS really has in Boston. All we know is that they have a few Vertibirds and at least one airship. And it wouldn't necessarily take particularly long to repair Liberty Prime. When they first brought him, they weren't just making repairs; it took them so long because they had to complete the design and resolve the power system issues. This time around, they have complete schematics, and they've had ~3 years to gather materials and conduct repairs.

Giant Robots are the dream of many men. If one giant robot can be built, then others can as well. Therefore, if there is a giant robot in Fallout 4, then it doesn't have to be Liberty Prime.

I fail to see how it "strongly suggests" the return of Liberty Prime. Surely there are other tall robots in the world, the history books of the Fallout universe are still being written. Bethesda doesn't need to rehash the same freaking stuff from Fallout 3. This is really reaching, to be frank, because even your pictures you shared of Liberty Prime's concept art do not at all strike any resemblance to the foot in the achievement picture. If it is a foot, then it's a completely different robot. See here, no concept drawing of the hulking robot show squared feet resembling the one in the achievement: http://fallout.wikia.com/wiki/Liberty_Prime