The new Virgin Resort is behind Planet Hollywood casino, not the MGM casino. Just walk East on Harmon Ave. The distance is about a mile.
It would not surprise me that MGM Resorts would build a new "Mirage". The rooms were not large, especially the cramped bathrooms in the standard rooms. To fix the room layouts would have been expensive. Probably not the best investment for MGM. So, MGM starting from scratch and making something better is a good idea. The Mirage has seemed a little run down lately. It definitely is not the prestige property that it was even 15 years ago.