Sources say that Busquets' next club, save any late twists, is expected to come from one of those three.
Messi's announcement on Wednesday that he has turned down the chance to move to Saudi Arabia or return to Barca in favour of a move to Miami could influence Busquets' decision.
The two spent over a decade playing alongside each other at Camp Nou and remain close friends, regularly meeting up in recent months when Messi has been back in the Catalan city.
After confirming his MLS switch, though, Messi said he was unaware of Busquets' plans and that their decisions were not linked.
"The media said I was going with Busi to Saudi Arabia, that we had it all sorted," Messi told Diario Sport.
"Everyone looks out for their own future. I am obviously awaiting [his decision], what he will do, but never in any moment did we agree to go one place or another. I made my decision and I don't know what he is going to do."
Busquets has also spoken previously about a desire to play in the United States, even name-dropping the possibility of moving to Miami last November.
However, as was the case with Messi, sources confirm that Busquets has been offered more money to move to Saudi Arabia.
Sources now confirm that Al Hilal, who had hoped to sign Messi as well, are also in the running for Busquets' signature as Saudi clubs continue to invest heavily.