Think of early personal computers in the early 80's. While the original Apple ][, TRS-80, and VIC-20 computers were cute, they weren't useful for much more than games and very simple word-processing and spreadsheet. By around 1984, the personal computer was pronounced dead by the popular press simply because virtually all computers were too underpowered to do anything. While many PC's didn't survive the industry shakeout (TI, Commodore), some did manage to find a niche. Today, computers are everywhere, but in a very different capacity than people thought they'd be around 1980. They're not controlling your house, and they're not vacuuming your carpet, but they found their place.
Furthermore, think of Object Oriented Programming in the late 80's and early 90's. When OOP first started to get a following when decent C++ compilers hit the market, the hype-machine hit OOP with all barrels. After the hype died down and the OOP settled into a mainstream niche, people pronounced it "dead". By that, nobody thought that it would disappear entirely, it just didn't meet up with the hype. Frankly, I never really understood how a programming language can take over computing, but that didn't stop Byte magazine from declaring Object Oriented programming "dead" around 1993.
3D, frankly, isn't a magic bullet. Think of conventional board games for a minute. Despite how cool and futuristic 3D chess looked in Star Trek, the half-dozen 3D chess efforts out there haven't even come close to unseating the 2D classic. That's because 3D, in and of itself, doesn't automatically improve things. For some games that are 3D by their very nature, like flight sims and auto-racing games, 3D adds a lot to the effect. To think that every facet of gaming would be improved by throwing 3D into it is simply ignoring history. There are board and card games that have survived for hundreds or thousands of years without a 3D update. There's no reason to thing that adding a computer would change the arena. Games are fun because they're fun to play, not because they look cool.
In conclusion, don't sell your stock in nVidia just yet. Just don't expect that 3D graphics is gonna be ubiquitous in every piece of game software. The microwave oven, it isn't.