Do I have any pops left in him or has his potential caught up with him yet?
You can try and see for yourself with a fast training for secondaries which take a very little part in potential cake. For example, 1 on 1 for Forwards; if he doesn't pop in DR or HA for at least 3 weeks, he's definitely done. If not, you can still improve his secondaries (DR and HA, PA). Don't forget Stamina and FT!