Who knows what level he will reach? The fact is, he is a good striker with plenty more potential to make good on, he didn't cost us that much and I don't think his one of the top earners. So the shouts to sell him are stupidity in my view. He's worth keeping even at his current level. Unless someone makes a huge bid, what would we gain in selling?
We shouldn't sell him just because a few armchair experts aren't convinced. When Aguero leaves, another striker is going to come in. When have we ever made do with just one? None of the top teams do that anymore. Even then though, people will have to come to terms with the idea that it's not likely we could get a striker with direct comparisons to Aguero and get behind who we have.
Ontop of that, I don't think people realise the rest of the team has to adjust to who is on the pitch too, midfielders and wingers will have to get used to which runs Jesus and whoever else makes and the timing of their runs. That in itself can make a big difference.