Hard to say. The way it was the discussion on the former chain, I wouldn't like it, because some important elements may be lost.

But the first candidates for pruning that I wouldn't mind if they were gone would be content (posts/comments/custom jsons) made by or for applications that are no longer around. Especially if those posts become unusable (for example, dlive, dsound). On the custom jsons side, we may have something like Drug Wars and other games that either failed or ended.

EDIT: On second thought, I don't think real pruning is possible. Because blocks are linked between them by hashes. And you can't remove blocks from mid-chain or you will break it. If you don't remove blocks, the size remains the same.