What is your opinion about Heroes IV?

If we develop the idea of a fourth installment, it should be made as a separate branch from the Might & Magic world.

No! Heroes has magic and heroes of the sword. And as I understand it, M&M is Might & Magic. If it's not like the third game, but it still contains everything related to swords and magic, then it shouldn't be separated. You're exaggerating, IMHO.