Karius is concluding the first of a two season loan.
The 25-year-old's strong finish to the season has seen him commit his future to the club when speaking after their recent defeat to Trabzonspor.
"This is a team game. I must not forget this, I am disappointed," said the German.
"Maybe we could have got a point. We have another game [before the end of the season] and a game to win.
"Then we will continue our preparations. I think that if all parties are happy and satisfied, I will continue. My contract with Besiktas continues."