Commander's Palace closed somewhat abruptly in early 2007. It was supposed to move from the former Desert Passage Mall at the Aladdin (now the Miracle Mile Mall at Planet Hollywood) to another (undisclosed) property, but that deal was, reportedly, scuttled by a breakdown in lease discussions.
While a reopening somewhere in Las Vegas is the intent, as of this writing, nothing is definite.
However, since this restaurant was so good and so popular, for good reason we're assuming that: 1) It will reopen somewhere; and 2) it won't miss a beat in doing so. A pedigree like Commander's earns the benefit of the doubt.