Its almost guaranteed the expansion will release shortly after Masters, maybe even the next day, worse case scenario a week later.
This is not a random guess, newer players may not know but this is the dev team's MO, they have done it several times, if you investigate you will find most expansions were released immediately after a tournament, and had a reveal campaign in the previous 2-3 weeks that finished with the last reveals during the tournament.
This makes great sense since they will be capitalizing on the hype of the Tournament aswell, a good marketing move for sure.
I hope we get some cool cards and tasteful changes to the already avaliable cards, the last changes they did really gave some flavour to the game, Harpies and Ghouls ftw !