It started a few weeks ago and last time I was there (mid-Sept, at in-law's house), there was not yet any detectable uptick in shorebird activity.
But...they were going to continue to draw down at a rate of 4" - 6" per day.
It might be worth someone more local to check out. There are not a lot of large tracts of public access, but there are many narrow easements (usually signed and numbered) that one can take to the shoreline and scope for birds. Idle Isle Park does sit on the north end of the lake.
It will not be refilled until next spring, so who knows that this will look like in the months to come, or say next March when the shorebirds come back through.