The survival of the Big East is contingent upon two things right now: don't lose anymore teams, and land a good TV deal. In fact, new commissioner Mike Aresco (a great hire, and NOT a Providence man!) is just who the Big East needed to take the reins. A former CBS executive vice president, he has all the years of experience and personal connections needed to score a sweet tv deal for the Big East. Perhaps the deal will be worth more than the ACC's; as unlikely as this seems, with the right sales pitch, Aresco may be successful in hyping up the conference enough to earn a million or two more per school than the ACC. NBC needs programming for its new sports network; they just might pay. It is also critical not to lose any more teams, especially Louisville or Connecticut. The loss of both could spell the end of the Big East, and would especially harm the conference in the basketball department. (ACC, if you're reading this, and if you want to kill the Big East, just steal Louisville and Connecticut.) Aresco must keep everyone happy, which may not be an easy task. A big tv deal would go a long ways towards keeping everyone on board, so all efforts should be focused there.
Suppose that, when the Big 12 does inevitably decide to expand to 12 teams, they will nab the two best possible choices available to them. The obvious and most likely option is that Florida St. and Clemson jump ship from the ACC to Big 12, robbing the ACC of two of its best football programs. The ACC may be gutted further by the SEC farther on down the road, but supposing that happens sooner rather than later, the SEC will likely grab North Carolina St. and Miami FL. Virginia Tech isn't going anywhere, being stuck at the hip with Virginia. That'll leave the ACC with 10 members, one football powerhouse in Virginia Tech, and... not much else positive as far as football goes. Georgia Tech could be good sometimes. Maybe North Carolina? Come this time, assuming the Big East is untouchable, who could the ACC add to get back to 12? No one, really, and they'd take a step back as a power conference. By that point in time, the Big East should be the 5th best conference.
There are a lot of teams in Big East football that have potential to be great every year. Boise St. is always great, it seems. Louisville, Cincinnati, and South Florida, all former Conference-USA teams, seem to be on the rise. Rutgers, the Big East's oldest member now, has been pretty good recently. Houston is a solid program as well. That's 6 teams who should find themselves bowling just about every year, with one possibly in the 4-team playoff if they run the table. Who knows who the Big East will add as their 14th football member; they may shock the world and land a team like BYU. Maybe Notre Dame will decide to move their football into the Big East, although that seems highly unlikely. Regardless, if the ACC is raided and the Big East remains intact, the Big East will find itself being regarded as a much better football conference than the ACC. The potential is there; games must be won and conferences must be realigned. Yet I don't believe anyone could argue this is not a possible scenario.
As far as basketball goes, I think the two conferences would still be pretty even. North Carolina, Duke, Syracuse, and Pittsburgh are the ACC's basketball heavyweights; the Big East will have Louisville, Connecticut, Georgetown, Notre Dame, Villanova, Memphis, Temple, and Marquette, to name, oh nearly half of the future 18-team basketball conference. The strength of the ACC's big four is undeniable; but Big East basketball isn't getting any weaker. New teams will have a chance to step up (ala South Florida in 2011-12) and ultimately, that will be a good thing for the league.