Board Thread:Warhammer 40k General Discussion/@comment-96.237.238.119-20131218020230/@comment-6078851-20140107010631

necrons could have a primarch lvl character(s) that hasn't yet awakened, or they could build something new of such potency.

tau will probably make a battlesuit in the near future that could contest with a primarch.

tyranids constantly adapt, so if tyranids start dying at the hands of primarchs then the hive mind will simply construct a new organism of similar stature.

eldar phoenix lords could, potentially, be reborn.

as for the orks - ghazkhull could concievably get bigger yet, although i doubt he would ever be a match for a primarch. but what about tuska the daemon-killa? an eternity of fighting and dying and resurrection. since he is never truly killed he ought to be near the size of a gargant, pretty sure he could go toe-to-toe with a primarch :P

primarchs could easily be returned. the greatest hero's of the imperium return to usher in the end of days to all threats....oh wait, this is 40k, everyone will always be a threat. the second the balance is broken would be the end of 40k.