Did Lamar Valley the other morning. You have to get a pass (not hard and only $2 for a vehicle).
Per Yellowstone's website as of yesterday the valley was not open.
Lamar Valley closed to public
The Northeast Entrance Road between Lamar Valley and the barrier near Warm Creek (2 miles from the Northeast Entrance), is closed to all vehicle, bicycle and foot traffic while major construction repairs are made. This section of road is an active construction zone, and the closure is expected to stay in place until Oct. 15 to allow contractors to complete work prior to winter.
Sounds like it's more of a partial closure than it being fully closed off. Guess when I'm there this month I'll just have to see for myself!