As long as we are watching Disney won't try. Votes are more powerful than money in politics when the voters are paying attention. Thus so long as we are paying attention Disney won't try anything. If we ignore the issue though...
Disney themselves according to shareholder reports also believe that Trademark law is in a strong enough position today that they aren't officially concerned about further copyright extensions when they can use the power of Trademark lawsuits to protect their IP. The copyright term is just one moat in their strategy, and they may indeed feel (as they've told shareholders) like they've made that copyright moat big enough they can focus on the next moat.
