I've got some serious doubts. While betatesting, I was gathering together the hero biographies to get some info about the HoMM5 storyline. To my great suprise, I discovered that in HoMM5 will feature a whole bunch of already known heroes (Christian, Straker, Tamika and few others) - apart from what was said before that HoMM5 will take place in a new MM universe, with a new storyline and logically - new heroes. My next shock was after I noticed that some of the hero biographies tell about Axeoth and Erathia! Let me quote:

Astral (Wizard)
Astral is one of the most ancient Arcane Mages, who remembers the times when Bracade was great. The experience gained during these years, and the deep knowledge of magic allow Astral to replenish his magic energy during combat.
Straker (Necromancer)
Straker is so old, he even remembers the time when he fled to Axeoth with other inhabitants of Erathia. In the passing years Straker has turned into a great military leader, but what he can do best is commanding corpses and zombies. These make the main striking force of his army.
(From a town biography) For many years Aranorn was in alliance with Palaedra, and Giadan is where the Elves and the Humans have signed their White Treaty. One of the tokens of friendship is Palaedrian army weapon - ballista; Giadan is the only town in Aranorn where one can get hold of it.
There are also several lines that allow me to make an assumption that in fact HoMM5 will take place about 20-30 years after the HoMM4 events on planet Axeoth.

Berein (Necromancer)
The only surviving pupil of Great Lich Hefas, Berein by right considers himself the successor to the former ruler of Necross Kingdom. The Undead recognize his rights and quite willingly join Berein who decided to restore the Kingdom of the Dead.
Great Lich Hefas must have overthrown Gauldoth's rule in Necross, and later died, while Berein became his successor.
[From a town biography] For many years Aranorn was in alliance with Palaedra, and Giadan is where the Elves and the Humans have signed their White Treaty.
Since new countries were formed after the civilization from the old planet during the armageddon fled to Axeoth, many years must have passed since that moment when Elwin and Lord Lysander made an alliance.

And there are few others.

My questions are:

1) Does HoMM5 really take place in a new MM universe or will it take place in Axeoth?
2) If it really is a new universe, how it comes the hero biographies mention the old universe?
3) If the main heroes of HoMM5 are supposed to be Isabel and Agrael who then is the Sovereign?

Agrael (Demon Lord)
Recklessness and hunger for power proved to be fatal for Agrael’s father â€" he was executed for taking part in a failed coup. The son had to work very hard to win back the Sovereign’s trust, but eventually he became his military commander. One of Agrael’s qualities which attracted the Sovereign’s attention was furious passion for battle.
As you can see, Agrael is only a servant of this Sovereign.