I think that we need to see how Keita settles before deciding that he is the answer. I think that they are a long way off being title challengers, the problems in defence that were there when Klopp arrived are still there. Maybe the problem is the players and chucking money at the problem will solve it. I think that Klopp isn't very good at this part of the game and the way he sets up a team will always leave them vulnerable in this league.
I don't think Keita is the answer, I think upgrading their keeper and buying a Wanyama/Dier/Matic type player for their midfield would be (somewhat) the answer. I'm sure Keita is an upgrade on Wijanaldaljum, as that guy seems pretty average. They would miss Coutinho massively though, so hopefully Barca will come in for him -- I assume that they will, to balance out the money spent on VVD and Keita.
As things stand, I don't think a lot changes for Liverpool.