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.
Robert Lewandowski is still one of the best striker in La Liga even now 36 years old, but he scored 27 goals under Hansi Flick which give them title once again sometime coach strategy also had impact on team performance so player not able to perform as they needed.
Xavi is also good coach but during his tenure mostly players were under pressure which bring some problems for them, but now things are back on track, and they are thrashing every defense which giving them good results now coming season is doing to be last for him at Barcelona, so things could be more interesting because Nico Williams is also under radar for Barcelona but how things will be ended it is not clear most chances Lewandowski will be at his best again for them in last season.