A little over a year ago, a group of physicists posited - and weren’t the first to do so - that time isn’t real. Basically they argued that the concept of time is “an illusion made up of human memories,” and since linear time doesn’t truly exist, “everything that has ever been and ever will be is happening RIGHT NOW.” So in a sense, Markelle Fultz is already back. In the reality we have constructed based around the linear passage of time, however, he’s not.
The Sixers released a medical update on Fultz today in which they did not give a timeline for his return (because, as I have noted, time is not even real anyway).