I guess I can sum my experiences thus: All the major Emigrant trailheads have commercial pack stations. Packtrain traffic is heaviest on either side of the weekend. Each commercial trip seems to involve two round trips--bringing the clients and gear in to a base camp, setting them up, heading back to the trailhead, returning to pick them up a few days later and again back to the trailhead. For a half dozen clients it seems to take a string of about two dozen head to get the job done.
Not all the horse traffic, of course, is commercial.
Leaving midweek and using the more remote trailheads are the strategies I recommend to avoid much of the hooved traffic. I find not so much their presence, but the profound damage they do to the trails to be the problem. But that's a topic for another day. I'd still go, because fall is beautiful in those meadows and if your timing is right, the trout will pretty much demand you toss in that lure.