I don't think we'll see it revealed this season but if it did happen and I had to vote, it would be in this order:
1. Ezra
2. Cal Kestis
3. Luke
Luke would be the easy option. He's alive at the time, powerful enough to sense Grogu's interaction and probably wants to save force users if possible. He'd get more people talking about the show too. But I think they would go with less popular options for a show like this. I think Ezra is the most likely since they're bringing in others from that show so it seems like he would show up eventually, one way or another. Cal would be okay but nobody would know who he is unless you played the game and even then, in the game he was still kind of learning his powers. He doesn't strike me as being good enough to sense Grogu and locate him after. I know there's wiggle room as to what happened after the game but still.
Then again, I didn't watch all of TCW and Rebels so I could be completely off with Ezra. Apparently he shouldn't be showing up due to how his story ended there. Anyway, I don't think it'll be Mace. They're already retconning a bunch of likely deaths in the Star Wars universe. Maul, the emperor, Boba. It's silly to keep adding to the list. They're entering anime storyline territory at this point if they keep it up.