I went for a hike there today with my wife. It was a good chance to scout the trail conditions for riding. We started up north at the top end of Pumphouse and went south to Boulder Garden, back to Pumphouse, down to the newly marked South-End trail to Sitting Bear to Wingdam and back across the north end of the lake to the start. Granted this is not my usual starting point (usually start on Cherry Ridge) nor does it include many of other nice south side single-tracks.
But, here is what I saw...
...the only dirt was on the north end of the lake. Otherwise it was anything from a sheet of ice to hard pack snow loaded with foot holes from hikers. The snow cover ranged from 1" to 6" deep still, with only a rare bare spot. Because of the colder weather today and likely tomorrow, it was hardening up and I could walk on top of the snow in most places, only poking through occasionally. But, again, there were tons of foot holes everywhere.
As much as I want to say its ride-able, the truth is...it would probably kind of suck. If you want to fight your way through, then I guess go for it on Monday/Tuesday while its cold. Or, wait it out for some more meltdown.
Hope that helps you decide.