Accessible as in the road being snow-free? I believe it is. I spoke to someone at Jackson Hole Mtn Guides today, hoping to get some route beta. They had taken a group out to Gannett from Elkhart Park last week (and are taking another group out this week), so I imagine the trailhead is accessible. Apparently, the first 6-7 miles are very muddy, after which the snow starts. The big stream crossing before Seneca Lake is tricky because of high waters - hiking poles will be handy there, I imagine. From there on, there's lots of snow, but it's mostly hard packed along the trail (for at least the first half of the day), so travel gets better after that. Summary: Lots of mud to start, lots of snow to finish, crevasses and schrund are well covered.