I don't think this will be more of an issue in 4E--indeed, probably less of one. Sure, characters can handle more encounters at a go, but that only comes up if you the DM throw more encounters at them. On the other hand, previous editions suffered serious balance issues if you didn't provide enough encounters per day to wear down the casters, whereas 4E is much more tolerant of situations where you only have one encounter in a day.
Not only that, but 4E power levels don't scale nearly as dramatically. In 3E, character power is expected to roughly double every 2 levels. In 4E, it's every 4 levels. So if your PCs are levelling at the same overall rate that they were in 3E, they're only gaining actual power--relative to their previous, un-levelled selves--half as fast as they were before.
That said, 4E will still suffer (even if not as much) from the problem that has plagued D&D since its inception, namely the fact that breadth-based advancement--expanding the number of mechanical options available to you--remains tied to depth-based advancement--increasing the power level of your best options. You cannot gain breadth without also gaining depth. So long as that stays the case, and so long as new/improved mechanical options are used as a reward for successful play, D&D will continue to be a place where PCs go from "regular adventurer" to "god-slaying avatar of destruction" in a matter of months.