Well the reason NV took only 2 years was because they took most of the stuff from FO3 and all obsidian did was add new characters weapons storys and quest, if they had used a new engine then it would have took more time
And thus why NV is 10x glitchier then F3 was...

I would love a Fallout 4 but who would make it? (Bethesda or Obsidian?) And, would they use a newer engine? (I pray to GOD so)
Once Skyrim comes out, I believe the thoughts will be hurled around their studio, at least i'm hoping. Fallout 3 was an amazing game, and IMHO, Obsidian ruined it by having a Perk chosen EVERY OTHER LV?
Honestly, that and not being able to make the Railway Rifle/Shiskehbab at a Bench is the only things I don't like about New Vegas in it's entirety...
But, if we can go to LV60 (once ALL add-ons are out), we can be like our Fallout 3 characters... technically.
I'd still MUCH RATHER have the system like Fallout 3. (Perk every LV up...)
I'm starting Honest Hearts right now as i'm typing this. I just beat Dead Money for the first time lastnight, and actually enjoyed (THE STORY), alot more then I thought I would...