Well actually if anything ti would be something BEFORE the Vongs. I mean the whole Shadows of the empire and living force era can be flushed out with many many new units. Also the New Imps and various versions of them all have different units, toys and styles.
If anything Vongs would be after all those conflicts. but IF VONGS EXIST, does it mean that we get to play with Chiss and Hapans? Oh, we can do the "molest Boba's daughter" thingy also?