If Melo's season is truly over, that means he finished with 41 games in a 72 game season. It is over half which wasn't the case in Embiid's season when he played only 31 games in an 82 game season, so I think voters might still keep him at number one if they feel no one else made the same impact Melo did. Although I think Patrick Ewing was the only one who won Rookie of the Year while missing significant time (only played 50 out of 82 games).
Honestly, unless Anthony Edwards starts putting up Kobe '06 numbers all of a sudden, that Rookie of the Year Award feels wrapped up for Melo.