Of course, they can't ever drop the Ransom teaching, which is the central point of jw theology, so they'll never accept human evolution. However, they could in the future accept evolution for the other animals, but say that man was an exception.
The stretching of the "kinds" definition is already happening. In the 2010 Life brochure, they implicated that the biblical "kinds" could refer to genuses, instead of species. So, it could be possible that they stretch it even more.
All of these, nevertheless, is fighting the facts in vain. "It is hard for you, Saul.."