Truthfully I think it will be an "M" rated game.

I mean with the Bosmer being cannibals, and the Dunmer having tons of slaves I find it hard to Imagine it getting even a "T"
However my big fear is that the developer is going to completely ignore these important pieces of lore in order to get a more profitable rating.

I should note I'm aware Morrowind was only rated "T"

That's anyone's guess.

It probably won't matter. Look at WOW. Most MMO's rules say you have to be 18 to play. Because of none monitored conversations between players. Maybe mostly because you are actually being billed for the game. Yet WOW seems to have 50% of it's players being under 14. An M rating just may get more kids to talk their parents into buying it.