I think all the suggestions of a compilation of the Complete XXX classes, the new skill uses, and/or the feats from those books are barking up the wrong tree.
The PHB II will most likely not be either a replacement or a compilation of material in other 3.5 books. I would expect that most re-printed material will come from Dragon or Dungeon magazine rather then other sourcebooks.
I would expect to see, perhaps, more combat options like an expanded version of the Dragon article on cinematic combat actions, the one that provided rules for swinging on ropes, riding counterweights, and toppling heavy objects onto attackers below.
I seriously doubt that any existing rules will be revised (getting up from prone, for example); that's the job for a revision or a new edition, not an expansion of the existing rules. Perhaps some additional feats to help mitigate the difficulty might be in there, but not a change to the rules as they are.