Voadam
Legend
I don't own the epic book but from what's been posted and what I read in the store, after 20th level caster level you go up in caster level but no more spell progression. loremaster and others increase your previous spell casting abilities on a 1/1 level or at a slower rate. It would make sense that when your 5 sorcerer 10 battlemage (where the battlemage increases spellcasting at 1/1) presumably 5 something else, gains a level of epic battlemage it will increase both caster level to 16 and spell casting (spells per day and spells learned) to 16 (because it is still under caster level 20). That would make sense to me but I don't have a rules reference for you.
Whether you can go sorcerer 5 battlemage 10 then take epic battlemage 11 at 16th level I don't know.
Whether you can go sorcerer 5 battlemage 10 then take epic battlemage 11 at 16th level I don't know.