Actually, most of those who post about those ideas have very little idea about game design, and therefore, the ideas sucked donkey balls (to be polite).
For a Fallout-like FPS, there's a number of mods around, being made, on hold, whatever. A FPS isn't quite Fallout's style, and stays where it is now, in mods and fan-made work. A post-apocalyptic FPS wouldn't be too bad, but it's not Fallout's or any other game's place to mutate into various other things without sense...much like X-Com.
As for the MMORPG, I've seen some really stupid ideas in the short while of seeing Fallout Online suggestions than I've seen in the more than 15 years I've been involved with MMORPG/MUD games. Basically, it's been nothing more than "I want a multiplayer Fallout." Well, most of those naive idealists haven't seen or understood what killed Origin and Ultima. To top it off, if there was a MMORPG, it wouldn't be called Fallout 3. So therefore any topics of that nature are to be posted on the Fallout Online forum.