Another ntr discussion, eh? I hoped we are past that point by now.
Well ... from Eric's point of view, Max is the one causing NTR. After all he steals Ann away from him.
From Max' point of view, so far there's only Kira and that only if they get caught at night. Not sure if Eric will steal anyone from him on friendship path or if Max shares willingly. The latter option would make more sense, since that's what the path is all about.
Eric will leave the house on each of the three paths. There has not been said yet, what the new challenges will be.
Some people are disappointed, that's for sure, but most people play war path anyway, so they might not be all that interested in Eric anyway or hate him so much that they went to celebrate for weeks.