From what I've heard of modding in ROTWK, modders will be able to code in the Arnor units (as in the units that were included in BFME1)
I have heard nothing else on the matter, and I've been keeping fairly up-to-date with it.
I personally very much doubt I'll buy it, unless I suddenly come across a huge amount of money somehow. I'm low on money atm, and with M2:TW coming out (aswell as other good looking games), I can't see myself buying ROTWK. Everytime I start to get excited about a new unit (DA Knights, Noldor Warriors), my excitement dies down when I see screenshots of them :(
I hope some modders do get the game though, just so they can give the community a good game, as I predict ROTWK being another disappointent :(