Hehe

Don't worry, they'll eventually bring the heroes to space.

Then we'll have centaurs with plasma guns against fairies with proton emitters.

And the heroes will command battlecruisers, somewhere in the middle of the campaign, when the Kreegans are really pushing us, the Ancients will arrive (and bring their Zips) hehe, and then Space Heroes Might & Magic 6 will be released.
Phantom Threat, War of the Vravar, Revenge of the Kreegan, New Hope (Nikolashka will return (Roland's son)), Kreegans Strike Back, and The Return of the Ancients :) Whew!

And in general, it's true that you need to know the history.

Almost all the creatures in Heroes are the result of an experiment to restore life in space after the war between the Ancients and the Kreegans.

The Might & Magic universe has different planes, and they must eventually intersect, and Forge would look very good, and if someone doesn't like it, then they're playing the wrong game; there's Disciples, or Warcraft, or Age of Wonders, or Warlords for them.

Added 10 minutes later
Or even Xin - it's an artificially created planet...

Honestly, there's still a lot of room for expansion in the third game.

After all, Catherine and Roland were on another continent (Jadame), and even if they were in Erathia, they could have easily survived.
Tarnum survived, and Gem and Crag Hack and Sandro... they just might have been transported to another planet... for example, to Ashan :) (just kidding).

Hopefully, everyone knows that Might & Magic is a multi-planetary universe