A couple of weeks probably, doubtful that it will take much longer than it did in Legion and that was 2 weeks.
Up for debate, and different for everyone. I’m not tired of ground mounts at all. I’m a little tired of not being able to use my flying mounts and I don’t particularly care for Pt2 as a concept (I think Pt1 is enough for the reasons they gave for starting this to begin with), but I only speak for me.
I’m unsure who the “we” is that you refer to, though. Maybe that person is tired of ground mounts in general. 