Didn’t the developers recently talk of possibly adding more kingdoms to the game? If that actually happens, then those kingdoms will have their own associated delve. That should be enough to push the max renown above 85k and gain that 2nd bonus magic.
Maybe they could use the already existing Vault and Primal kingdoms and just add them to the map. I mean they already have associated troops so the devs don’t have to completely start from scratch. Plus it would give us an opportunity to gain a gnome and an elemental class for the hero.