he turned 28 few weeks ago, no way imo we get 5 great seasons out him but also doubt Pep will be here in 5 years time so he wont care the state of Kane in 5 years, he wants Kane for next two years and rightly so as we need a top striker who we can rely when others just cannot come up with the goals especially if they do not have the killer instinct or lose form like Sterling. Magical seasons like Gundo just had also wont be repeated as its a rare thing.
Strikers who played majority of their career in PL dont tend to bet that effective after around age 31. the tempo, the speed of the league, the constant lack of winter breaks years after years especially for top teams playing on multiple front with lot of extra cup games and international games, its more a surpise if a striker like that still bags in 20+ goals in PL.
I was quite sad to see Kun in his last 1.5 year I think PL left its mark on him big time and I doubt he will be able turn it around in La Liga and rebuild himself. he couldnt really catch a good break even since 2020 January.
loss of pace, physical ability, more and more injuries, and given Kane is not that athletic type like CR or Lewandowski who are both beasts at an older age I expect 3 great seasons from him and then 4 if he is lucky with injuries overall. Southgate will overuse him in England games in next 2-3 years as captain thats almost certain and because alternatives does not come close to him really. (Calwert Lewin, Rashford?)