Well, this will be a golden opportunity for Kepa to leave Chelsea and of course he will be very happy to be part of Real Madrid again. Maybe he also doesn't care about the competition to be the main goalkeeper at Real Madrid and the most important thing is that he can continue to win titles. What's more, he will also be very close to his family in Spain.
Apart from that, considering that Lunin still wants to leave if he doesn't get the chance to play as a starter, it is very likely that he will move before the summer transfer window closes. He will be the target of many clubs and I think the team that can sign him will be very lucky.
Lunin's contract will expire next season and until now there is still no clarity on this matter although in some statements although not explicitly but I think Lunin still wants to stay at Madrid but the decision is of course in the hands of Madrid for now whether they will extend Lunin's contract or not.
It's just that if the choice is with Kepa then I think it would be wise enough for Madrid to keep Lunin and give him a new contract especially with the performance he gave this season when replacing the injured Courtois then of course Lunin has the potential to continue to be able to get good performance in the coming season.
Kepa is not a bad goalkeeper but in recent seasons he has experienced a decline in performance and I think if the choice is only Lunin and Kepa then Madrid will definitely choose Lunin.