2021/22: Amanda Gorman (co-chair), Pregnant Rihanna / Gilded Glamour (In America) 
2020: Gal Gadot / About Time 
2019: Kim Kardashian / Camp
2018: Amal Clooney (co-chair) / Heavenly Bodies
2017: Katy Perry (co-chair) / Kawakubo
2016: Taylor Swift (co-chair) / Manus x Machina
In conclusion, we most likely will not get a solo model cover - especially a model like Luna or Vittoria whose claim to fame is primarily fashion based. Bringing back a retired supermodel like Claudia is more up Edward's alley, so I would rule out that possibility as well. My bets are on one of the co-chairs, as seems to be the tradition in the past couple of years. This year it's Dua Lipa, Penélope Cruz and Michaela Coel. Coel had a cover recently, so it probably won't be her again. Dua had a cover last year, but I would say that she is the one most likely to get it. Cruz would be my personal pick as she is the one with actual ties to Karl's legacy, but that doesn't seem to be a factor in their cover subject selection (or co-chair selection either, apparently). 
It would be a gag if Anna ended up giving the cover to Federer lmao I wouldn't mind at all.