There's two ways to look at this. Personally I want us to keep our best players as long as possible and build teams around them.
The other way is to look at it similar to Lyon around 10 years ago. They would sell players when they peaked and replace them with top quality young players, then sell those players when they peaked, etc. That method allowed them to bring in massive money and ended with them being CL regulars for a good few years. They regularly got past the group stages of the CL.
We could sell, for example, Coleman, Stones and McCarthy for a combined £80mill having spent £16mill in total on them.
Like I said, I'd rather we kept all our best players but if we had a strategy of buying young and selling when they reached their potential we'd at least know what to expect. It might be an alternative to carrying on waiting for a takeover too.