This is such a SMALL amount of area they are using for the play area that I have no problem with it (assuming ithe play area is just within the bordered fake rock area as pics posted above show). In fact, I wouldn't even consider a replacement for the 20K LUTS at all. If themed nicely, it could be a nice little diversion for small children inside Fantasyland.
The area that it occupies is just one small area of the old lagoon. Remember, the entire area, including the very large showbuilding for 20K is open for something new. Take a look at some of these arial pics, courtesy of disneypix.com, to get an idea of how big this area really is:
http://www.disneypix.com/2000ft/Roll4/Roll04_003.htm Notice the very large showbuilding next to the toontown tents...that area is now just empty land waiting for something new. The new Pooh's Playful Spot would take up just a small corner of the old area of the visible lagoon.
Take a look at this pic for a comparison shot:
http://www.disneypix.com/2000ft/Roll4/Roll04_004.htm That area where the old 20K showbuilding appears as if it were as big if not bigger than the showbuilding for Small World or the Haunted Mansion (but obviously a lot shorter in height). They could easily put a queue in the area that is left of the former lagoon, still keep this Play area for kids and still have an enormous area to build a new attraction.
I'm still waiting for that something big. I patiently await that annoucement. To spend all that money and time to reclaim that large area now, vs later, seems promising to me.