Injustice 2 was released last year and most of us really enjoyed what Netherrealm Studios had to offer. Since then, plenty of new characters and arenas has been released, not to mention the Ninja Turtles. If you still haven't gotten the game, it might be an idea to wait for a little while as it seems like a Game of the Year edition with presumably all the DLC is about to be announced.
This was revealed by both Amazon and a Malaysian retailer, before they were removed shortly after. Fortunately, people saw it and you can view the cached Amazon pre-order page on this link and the Malaysian add below. It is supposedly released on March 27th and although nothing has been announced, this one should be filed under 'highly likely' as it will likely arrive sooner or later anyway.
Update: Warner Bros. has now confirmed that Injustice 2: Legendary Edition will indeed launch on March 27 for PC, PS4, and Xbox One. It will include all the released DLC characters and some premium skins. It also adds an expanded tutorial, new gear items, an increased level cap (level 30) and an additional augment slot (unlocks at level 30). Whether these improvements will be implemented in the base game remains to be seen, but it sounds strange if they're not.