Bob Burns' last day open to the public is May 31 (tomorrow! as I type this)--I was there Monday evening for dinner and that's what the sign on the door said. (It was pretty crowded and is probably packed all week.) I'm not sure when the Houston's is going to open.
It is a shame that such a unique place will be no longer. I believe there's a private party for staff and friends that will be held Friday night. If you can get there tonight or tomorrow, even just for drinks at the cool piano bar, it's worth it. This place is of its era and anything that replaces it will pale by comparison.