The carriers that were in T3 before VX kicked them over to T6 (where VX was before they came to T3) will likely come back to T3, so I wouldn't get your hopes up that VX will take over the terminal.

In addition, VS isn't likely to come to T3- no customs and immigration station, which is one of the reasons why AS wants out (aside from their side of T3 really being T3rdWorld, and wanting to be closer to their new partner DL in T5- right now it's a LOOOONG walk or two bus rides).