I have two Rock River Arms lowers here, I also happen to have two VLTOR collapsing stocks here for the sunset in September. When the sunset happens, and I put the VLTOR's on, will I have to put uppers on them to make them into complete rifles incase another AWB comes swinging by, or will they be grandfathered in? My guess is no. I won't be able to afford uppers, atleast I don't see it, but anyone want to clear this up for me?

That would depend completely on the wording of any new law that may come along.
Until there is a law to reference, there is no way to answer your question.

Pretty much answered, but if you want to make sure you had a "complete" firearm, having one upper, even if it was "given" to you and you "gave" it back, attaching it to each of the lowers, would be compliant with the previous ban.