While a stadium on-campus in Storrs sounds great, it will not happen because 1) the land targeted for the stadium is now part of the Tech Center development, 2) the roads around Storrs cannot handle traffic to/from Gampel, which holds roughly 10,000, never mind a 50K stadium, 3) the state pumped millions into the rent less than 15 years ago, 4) the state is really bad financial shape and will continue to be so for a while, 5) and an on-campus stadium may draw less non-students due to #2 and because it if 30 minutes farther from Fairfield County.
I honestly do not think a 40K stadium is a major road block to joining the ACC or (praying to whatever deity works) the BiG. As long as UConn has passion, i.e. can sell it out, which is not the case today, and focus on football (practice facility good, PP as coach bad), The Rent can be expanded down the road when sell-outs become an issue.