Mark vs Gohan is far from out of the running, and Invincible's second season coming soon has me honestly thinking Mark vs Gohan has a higher chance of occurring, simply to capitalize off the Invincible series returning hype.
Hit's only chance of showing up again and doing anything relevant, is in the anime, whenever it may return, and that's no guarantee. Definitely won't happen in the shitty canon fanfic manga, that's for sure, given Toyo's terribad writing and the way he treated Hit, which made him look like ten times more of a scrub than he did in the anime TOP.
If not Jin(And not Moon either, unless they'll pull double duty on her, very soon following Madoka) that only leaves, what, Pegasus Seiya, as an alt? If so, oof.

ha