For the next two seasons I believe Lewandowski is still able to play at a good level but Barcelona needs to find a replacement figure because it is feared about the injury experienced by him.
He can be a distinguishing figure in the team because of the maturity and experience they have so that this is an advantage for Barcelona.
Age can indeed affect speed a little but if Barcelona has a number of creative midfielders it will not be difficult for Lewandowski to play at a better level.
A substitute figure can be used as an alternative because the coach can more easily rotate and I think Barcelona does need the figure next season because they will play in many competencies.
Lewandowski is that one player any team will count on any day any time, like dude is damn good at what he does, believe me lewandowski can still perform pretty good in the next three seasons coming, because dude is a baller, like we've seen lots of players that is good as lewandowski and even at their 30's they were still doing good, the likes of Ruben, xavi, mudric, etc.
So I still believe he can do it no matter the age, or maybe Barcelona should just get a plan b Incase of injuries at least the plan b can come in, but talking about if lewandowski can still perform I'm 90% sure of that.
Lewandowski is indeed a great player but there are times when great players like him lose their sharpness if we remember the previous season when Barcelona was in the hands of Xavi he was not so productive and many people criticized him and said that he was old and his speed was starting to decline but when Barcelona changed coaches he seemed to find himself again and started to be productive again so I also believe that as long as he is coached by Hansi Flick he will most likely still perform well unless he suffers a serious injury that will interfere with his performance when he recovers.