My uninformed guess would be that a women's team will come before the stadium opens though possibly after it is announced (let's not forget that if the stadium is built properly and not rushed then there's at least an 18 month period between announcing the stadium and actually opening it, and that's assuming that work begins the day it's announced). I would assume that NYCFC II and NYCWFC would share a stadium rather than each going separate ways, although that is assuming the club finds a stadium to take over rather than sharing with an existing facility. If NYCWFC end up playing at Columbia University, for example, it would be unlikely that the club and the uni would want to shoehorn in a second professional club too.
I could possibly see the two playing at a club training ground although possibly not. Any training ground must logically be close enough to the city for the first team to train there - that's only common sense. However, that means that the training ground must be somewhere close enough to the city for the horrendous property prices, land availability, NIMBYism, etc to apply. In these circumstances I find it likely that the club would struggle to fit a full-sized training complex in plus a stadium with capacity to fit in several thousand fans - I don't see them wanting huge bleacher developments on their main training pitch either.
The idea that NYCFC II could play further afield is possible I suppose - this is something where US and European teams differ as a European team would never put its reserve team outside of the community its senior team played in, so I don't really feel qualified to comment on whether this is likely as my own bias/experiences affects my thinking. If that happened I have no idea if the women's team would move to match them or would stay in the city.
