We stayed there last year December. During our stay they were decoupling Avani+ from Anantara and AVC (i.e. first days we could choose where to have breakfast, later we were only allowed to have breakfast at Avani+). They also told that eventually it will be treated as 3 separate hotels (although while staying at Avani+ you could still use the Anantara beach) with each there own facilities. So I doubt they will shift reservations between them. Regarding the upgrade, I was not upgraded proactively, and had to ask for it while it was not busy at all (we did get late check-out).