Last time this happened, about 4 yrs. ago, or so, it must have taken well over a month for the area to dry up with all of the tire tracks running through it and holding water.
To spare yourself a very muddy bike, or muddy shoes, your best bet is to follow the alternate paved route shown on the map through Cougar Village until it firms up a bit.
The St. Charles GORC crew, and St. Charles County Parks never stop! They just keep adding more and more trail at Matson Hill. As a result of the spring workdays, another 0.6 miles of trail is ready for you to ride. Please respect the signs, and turn around and return by the same route, as requested. There are a couple of workdays scheduled for Matson in the fall, so if you want to see more trail like this, please volunteer.