>>212694246 (OP)No. He lacked the constitution, virtue, and disposition. At his age, he'd never become good.
With the right court around him he could've been refined into a halfway decent king though, especially without the civil war and losing Tywin.
>>212695072 is right that Tommen's youth would have been a huge advantage as long as Cersei is boxed out. Margaery would have been a very able pseudo-regent and a good teacher.