It wouldn't be ripping off Fallout 1 though, that's like saying NV ripped off the entire Roman Empire with Ceaser. Someone could have learnt about the past and re-do it. Bethesda doesn't put original fans first with their games at all, I would say 60% of people who played fallout 3 and New Vegas haven't played anything earlier than that, so it could be very likely that they bring back an FEV/something similar to Fallout 4.
New Vegas didn't rip off the Roman Empire. It isn't even a fair comparison. To have another Super Mutant Army yet again threating to destroy the Brotherhood and take over the wasteland would definitely be ripping off Fallout.
Many people on here started with Fallout 3 or New Vegas and have gone out and played Fallout, Fallout 2 and Tactics. There is no reason why other people can't do it.
There's not really a huge amount of things they can do, and it will never please everyone, I just think it could be done well and if it's all in a new setting could be interesting.
I am not a big fan of Bethesda but I still feel if they put their minds to it they can come up with a unique story of their own, with totally new factions such as the Commonwealth which should have played a much bigger role in Fallout 3. But saying "there's not really a huge amount of things they can do" to me shows you think Bethesda can't think of anything original.
What you are asking for is just the samething over and over again, or worse a complete reboot of the series which would also mean Fallout 3 and New Vegas needs to be rebooted.