For that matter, why isn't there a clear separation between Tomorrowland and Fantasyland? That are right at the transition has always taken away from the magic.
The two areas could definitely benefit from melding together a bit better. Once Tomorrowland became based on what the future
could have been rather than what
will be it fit well enough next to Fantasyland. Despite the science-fictiony atmosphere, just about all the attractions are based on purely fantastical concepts when compared to their previous incarnations(magic monster portal doors, living toys fighting in space, etc. vs. human flight, time travel with a time machine/robots, etc.). If they blended the colors, buildings, and landscaping a bit between the two places I think they'd clash a lot less.
Profits drive the equation.
So, my thesis is that the marginal changes that this thread has suggested will not occur any time soon. Oddly enough, you seem to agree.
Unfortunately, Disney World Execs have a different philosophy. I don't think they'll make any major overhauls soon. With the New Fantasyland bringing in the crowds and the revenue, I doubt that the execs are entertaining any major expansion or remodel ideas for the near future. However, I sincerely hope that in this time of prosperity and ever increasing crowds for the parks that they will at least refurbish the old neglected rides that are in such need of some TLC.
You've both hit it on the head. The supply currently more than meets the demand, the execs have no reason to invest anything else in MK at the moment.
The NFL expansion was massive as was the implementation of the magic band system (not park exclusive but a huge money sink) and the expansion of the Castle hub. Reinvestment in each park is theoretically not a zero sum game but realistically the head honchos are going to be looking at ways to justify ticket price increases in the other three, currently underutilized, properties in the resort.
Partly due to the overhauls and construction in the other parks, I really doubt we'll see MK get anymore major changes for at least a decade. Maybe we'll lose minor things that don't need replacing immediately and gain a new gift shop or even a restaurant or two along the way.
Something like removing the Rivers of America and filling it in or taking down Stitch and rebuilding from the ground up would be monumental monetarily. Honestly, as much as I'd love to see some things change in MK I'd rather they divert the time, effort, and money into building and updating Epcot, AK, and HS. Especially Epcot, every time I walk into the old Wonders of Life pavilion during the festivals and catch a glimpse of the old entrance to Body Wars my heart breaks just a little bit.
Or maybe they could spend some of that money to beef up security at the Food and Wine festival because the crowds become more belligerent every year. 
