The whole "breaking off the NCAA" mantra is the most oft-repeated and overstated narrative borne out of realignment discussion in the past three years. It's really not the foregone conclusion that people are making it out to be.
There's really not the incentive people think for it to happen. People forget that these conferences ARE the NCAA. The NCAA is a membership organization that is controlled almost purely by the NCAA presidents. At the Division I level, it's the Division I presidents that vote and FBS presidents have a weighted vote in their favor on all voting issues. These major conferences already largely control the NCAA governance.
As far as the revenue: it's way overblown. The power leagues have already split from the NCAA. It's called the BCS. If you recall, the BCS is completely, totally and utterly independent from the NCAA. The money is split how they want and with whom they want. The only thing the NCAA approves is the number of games played within the season, how many bowl games are approved and how the programs are operated. Beyond that, these schools already control the revenue and where it goes. And interestingly, they voluntarily funnel some money to FCS schools despite the fact they have never been under any obligation to do so by the NCAA structure as a whole.
While it's certainly possible they could elect to have their own autonomy, it isn't likely. If they do, it will be for football only and they'll remain part of the organization for all other sports. The money from the NCAA Tournament is more than they'd receive by breaking off and doing their own thing for basketball. That's too big a piece of pie to leave on the table. More likely though, they'll do what they've been talking about at the last three years of meetings: creating a third sub-division in football.
The only real incentive at this point, to breaking off, is having a playoff where they don't have to automatically include the other FBS leagues. But when the difference between the haves and have-nots become large enough, there has already been a proposal within the NCAA to create a third-subdivision. This will allow the power leagues to have a playoff that includes their own 8 teams and share the revenue in a capacity that more closely mirrors the NCAA Tournament. If the third subdivision does happen, and again the power leagues have already been discussing this with the other leagues, then it will eliminate the last real reason they have for leaving the NCAA structure.
I won't make the mistake of saying it "won't" happen. But I do have a good, educated hunch it isn't what they're planning. And I do know it doesn't make as much sense to do so as people talk about on message boards. I'll be surprised if they go that route. If they do, it will simply be a separate football organization that still allows for scheduling of NCAA schools.