I think he'll do pretty good. Top 3, and if stars align closer to the top. I hope his obvious brain farts in Moto 2 are a thing of the past. GP is extra serious and I think Nakamoto and HRC will have focused on this part of his preseason preparations. His riding talent is obviously above that of the past years GP rookies. Being on a top team with a top bike should ease wins and a possible tittle bid.
If Dorna, Ezzy, or the behind the scenes powers that control GP racing have seen in Marquez the future and the future champ, then props to Marquez and his family for putting himself in that position. I think that in GP he will be much more accessible to the international market in terms of public appearances and hope this will show his personality. Here in Spain he is not at all seen as the petulant, arrogant golden boy it seems he is seen as here on PS, and an international level. That spot is reserved for JL around here.