You'll probably never do things the people who contributed won't agree with. But someday you'll pass away, and the people who end up with your estate might not care about the intricacies of software and sell it off for cheap to somebody who'd rather do anything to get a return in investment.

Even if the CLA somehow said you could only relicense to MIT, they could simply do that without releasing anything, and immediately take it and use it in proprietary things :)