I think original voices rights could be the biggest issue.
I wouldn't mind to see the games re-released with the HD collection voices... But I don't know if it would be possible (on technical or legal point of view).
Oh right, there was that whole ordeal with the voice actors, but in the end, this got resolved for 2 at least.
Also, the HD collection was basically a new game, while releasing the PC ports here would be a mere re-release of a game for which the usage of these voice actors has already been dealt with, right? Not sure how this works.