Liverpool had reportedly given up on signing Keita this summer, after seeing big money rejected by the German side.
A clause in Keita's contract means that he could be available for £48m next summer and, while reiterating that the midfielder will not be sold this year, Rangnick does not expect Keita to sign an extension.
"I am not now assuming that we will be able to extend his contract prematurely", Rangnick said.
The new contract will not only see a significant increase in wages but will also remove the £48 million release clause in Keita's current contract.
"But I can assure everyone that Naby will play for us this season. All other scenarios also depend on how we do this season, how Naby plays himself and so on". "We want to be successful in sports".
The Guinea global made 32 total appearances across all competitions and played an instrumental role in helping Ralph Hasenhuttl's side to finish second behind by Bayern Munich in their first ever season in the German top-flight.
Only Forsberg, who assisted more goals than any player in Europe's top five leagues, created more chances than Keita for Leipzig.
"He is more focused on us and has more fun now than previous year".
Only Borussia Dortmund playmaker Ousmane Dembele, the France wonderkid Barcelona are desperate to sign, dribbled past more opponents than Keita last season.
Liverpool have agreed terms with the player, but at the moment Leipzig have batted away all their offers.