I'd heard that they were thinking of making a whole series of Iron Man movies, and read a quote from RDJ saying he'd do 15 of 'em, because he's a huge Iron Man. That's a lot, but if they did several, it might not be too awful if they explored Stark's problems a few movies down the road. In the Marvel Universe, this is what happened, and Rhodey took over for a while (which is why he looked at the suit and said "Next time"), so it would be canonical.
Once the franchise has been established and kicked ass a few times, it might not be bad for a change of pace. But doing it in the very first sequel would be a mistake. They need to build a little more momentum up first.