I personally know about 40 people who aren't going to touch the game until custom servers come out. The MP player base won't be split, instead thousands of players will return to the mods they know they will like.
And I personally will be bringing four people i convinced to buy Bannerlord who never played Warband. They didn't like THE MP, so I advised them to wait for the mods.
That being said, I don't know what is going on at TaleWorlds. If they need time to ensure that custom servers won't crash, or mods won't need to be updated every week, then I'll just have to be patient.