Tbh regardless of what his long term plans are for Aguero I'd rather see us hold onto him in the summer and use the money to strengthen areas that are more in need of it - every club knows that we'll be desperate for full backs this summer so we won't be getting them cheap and that's after the £55m or so we look like we'll be spending on Laporte. We won't replace Kun with like for like quality this season and we won't get a fee that reflects his value to the club, I'd rather hang on and sell him for £40m the summer after than sell him for £70m this summer.
Besides, the best option overall is to work out a way to accommodate all our current forwards - I think the idea that Aguero can't play in Guardiola's style is rubbish - go look at the home match against Barcelona for proof of that, it was the perfect Guardiola no 9 performance. Whether his muscles will allow him to do it week in, week out is anther matter but that's less important is Jesus can step in to cover him.