FO3 was a very successful game, and bethesda has two franchises they develop themselves, elder scrolls and fallout,
While that's true for the Elder Scrolls series, the only Fallout game in the series that Bethesda Game Studios got to work on was Fallout 3. What I'm saying is that the franchise, Fallout, is all thanks to Interplay and Tim Cain (who happens to be working for Obsidian at this moment
) who started the series with Fallout: APNRPG. Fallout 2 (the game Chris Avellone helped design) was
published by Interplay, but developed by Black Isle. Basically, don't believe that Bethesda is the "all mighty original king of the series".
Um...what? ...No.
FO3 will have a sequel, called FO4. so new vegas was an extra fallout game because of the success of FO3,
Wow, so what is this future seeing technology you have and where can I get one? Fallout: New Vegas was not an 'extra' Fallout game. I've heard this argument many times before, but Fallout 3 is totally irrelevant to Fallout APNRPG and Fallout 2. I seriously have no clue why they named it Fallout 3. It's on the complete opposite side of The States for Christ's sake.
Fallout: New Vegas, on the other hand, picks up on a lot of stuff from the classics. It's based on the cancelled Fallout 3 project "Van Buren", (designed by Chris Avellone and JE Sawyer, who also work for Obsidian) and has a lot more to do with the classics than Fallout 3. Which is why I feel Fallout 3 should have just been called Fallout: Capital Wasteland, or something. Fallout 3 feels like a spin off.
This is going somewhere, stay with me. Chris Avellone and J.E. Sawyer both worked on New Vegas and they are currently employed at Obsidian Entertainment. Just recently Tim Cain (nudge nudge) joined the team. I hope you can connect the dots, but what would it look like if Bethesda had BGS develop the next game in the series with these 3 devs right out there too. I'm going to say that Bethesda is probably going to let Obsidian develop the next game. Probably.
My point? Don't count on seeing the Capital Wasteland sometime soon. It's just unlikely. Hell, we don't even know if there are plans for a new game.