Subsequent updates will garner diminishing attention in playtime and sales, people that did not like it enough will likely drop out and not return, even after EA. You could say it is a success in sales right now, but not a successful game. Depending on how the EA goes it might also increase or hur the company's reputation for potential DLCs or the next game.
DOS 2 saw the overwhelming majority of its sales after the year-long EA concluded and the game actually released.
I see absolutely no reason to expect something particularly different here. Except on a much bigger scale, given that it's already over a million now, which is a number DOS 2 couldn't even dream back then.
