>new expansion
I expect every faction to get at least 1 new playable deck with some getting a bonus one too. They're basically doubling the card size. Usually base/1st sets are very big so expansions do very little to the game unless they contain multiple good cards, but in SV2's case the set is just 140 cards, adding another 140 should do a lot to the game.
However, I doubt we'll have more than 4 Tier 1 decks still, the powerlevel will also increase. However some Tier 2 decks will hard counter Tier 1s.