Sterling doesn't have the end product yet - but he's a more Cesc than Lennon for me, in that he looks the sort of player that will develop in that direction within a few years.
I'd happily take one of Zaha or Sterling, though neither are ready to replace Theo yet. England are going to have a quality attack in 3-4 years.
There's no way Liverpool let Sterling walk now, anyway, unless they have serious concerns about his attitude (which I doubt)