No, they need to build compelling reasons to go to the other parks while you're at WDW.
MK didn't have these insane capacity problems before EPCOT and MGM fell off. The park has always been the most popular with the most to do, and while it needs work the existing imblance cannot afford to be exacerbated. Reopen existing facilities, sure. But they need to take some time and get the other parks on its level, or closer at least. Otherwise Magic Kingdom will only continue to give guests more reasons to come and things to see while the other parks atrophy on their underbuilt/underutilized infrastructures.
MK can hang on while other parks get investments. Its popularity isn't going anywhere and those crowds *can* be mananged by the existing park. You can't keep feeding one child and wonder why the other three are starving.
Not that I foresee things happening this way, mind you. MK does have projects on the horizon.