I understand that some loved Millionaire. Personally, I think it is the worst thing Disney has done since the openeing of DCA.... It had absolutely NO entertainment value for me, and another "game show" type thing has NO interest from me.
Disney is HIGHLY unlikely to build anymore 'edutainment-y' rides... They have proven themselves non-cost-effective time and time again. No staying power. I understand that some people really like those rides, but look at it realistically. How many cartoon based rides have closed in Disneyland... Disney World? How many edutainment-y rides have been replaced, redone?
Of the rides likely to be built, Mission:Space is the top of my list.