How can I contact the developers of Heroes of Might and Magic IV?

I think it's purely a financial decision (they bought the franchise with all its assets), because they don't have the brains to revamp the fourth installment – they're stuck in their own world.

The main point is that they are the rights holder, and that's all.
I don't know if they have the brains for it, but either way, they outsource the work, acting as a publisher. But they are unlikely to be genuinely interested, and they won't do anything just for fun.