If a firm is asking for references before you’ve got an offer, is that a pretty good sign they’re going to offer you?
If the firm is asking for references before you get an offer, then it probably means it is more likely than not that you will get an offer, but I would say your odds don’t increase higher than that based on the reference check alone.
When I lateralled the firm I was interviewing with asked for my references before my first in-person interview, just as part of filling out the paperwork. So I don’t think it meant anything in that scenario, but who knows how this firm handles things.