That will happen pretty definitely.. why should a developer create games for an outdated console (even if it has millions of users)?
Maybe because they have millions of users? Not to mention much lower development costs.
Yes but a state of the art game takes years to develop.. years during which most people will buy the new console and after 2-3 years of development you may find your playerbase for the old console has eroded and half or more of the people have switched to the new one.
Current games in development won't get cancelled but once the PS4/XBox 720 are released later in the year i guess most developers will switch exclusively to the new machine. It's just not profitable in the long run to develop for a soon (in financial/development terms) to be outdated/outclassed/unsupported/not sold in major stores console.
Would you as the CEO of a videogame corporation approve a PS3 game now knowing that in about half a year there will be a new, far more powerful machine available?