No, no, they just completed the largest expansion in Magic Kingdom history with the Fantasyland expansion!!! Lots of space for MORE MAGIC!!! MK has no capacity problems at all now!!! And with the new projection/laser/light show (with some fireworks sprinkled in so they can still call it a "fireworks spectacular"), MK will be MORE MAGICAL!!! than ever before!!!
More people go to MK because there's more to do there than at the other parks combined, in essence. Until Disney fixes that, nothing's going to change. Sure, their current big-price-tag projects - Pandora and SWL - will funnel some people away from MK for a while, but after a few years, I bet we're still looking at the same problems at MK unless there are some significant projects/changes/additions in the works. Yeah, I know Martin has hinted at some major improvements for Epcot for the 50th (and that's so long-overdue it's not even funny), so maybe all of that together may make a dent, but I'm not holding my breath.