Hedging my bets for next season, by ranking how likely the super-requested matchups are. Let me know if I left any out, or there's any you disagree with.
Basically lock-ins:
Giorno vs Joker (given how requested it is, and how well DIO vs Alucard is doing view-wise, I'd be more surprised if we didn't get a Jojo matchup next year).
Thor vs Vegeta (Dragon Ball and Marvel are evergreen franchises for Death Battle, gives us the chance for a modern Vegeta analysis. Very algorithm-friendly too, which is a plus).
Ant-Man vs Atom (probably the single biggest Marvel vs DC request at this point).
Cole vs Alex (assuming not this season in place of Galactus vs Unicron).
Jason vs Micheal (assuming that COVID regulations have relaxed to the extent of allowing it to be filmed).
Catwoman vs Black Cat (I'd argue best bet for the next Marvel vs DC street tier fight)
Probable:
Bowser vs Eggman (the single biggest Mario vs Sonic matchup left to do, gives them a chance to give Bowser his due after the agony that is Bowser vs Ganon. Could also be the first 3D fight to feature either a Mario or Sonic character, so that's something).
Simon vs Kyle (It's THE Death Battle community matchup at the moment. More a matter of if than when at this point).
John vs Raidou (The upcoming episode is sponsored by SMT5, it's decently requested, Raidou is more relevant recently with the Nocturne remaster).
Scarlet Witch vs Zatanna (Marvel vs DC, WandaVision, blah blah blah ... ).
Fire Emblem as a whole (one of, if not, the single most overdue franchise for Death Battle (alongside Hunter X Hunter), plenty of viable characters and matchups)
50/50:
Mewtwo vs BlackWarGreymon (best shot for a Mewtwo runback (runback in this context refers to good episode. not winning), decently requested, grants opportunity for new analysis for both Mewtwo and Digimon as a whole).
Master Chief vs Doomguy 2 (the single most requested remake now Link vs Cloud is out of the picture)
Captain America coming back (has good opponents (Kamen Rider Ichigo would be ideal for me), his main story in the MCU has concluded, there's never been a better time to use him).
Ridley vs Rayquaza (there's been a decent influx of new opponents for both characters (I'm personally an advocate of Ridley vs Vile) so this one's not as likely as it once was
Spiderman coming back (mostly capitalising on Spiderman: No Way Home hype, but I'll say we're about due another Battle Royale).
Omni-Man vs Bardock (capitalises on Invincible viewers, Ben's said that he's not a fan of Omni-Man vs Homelander).
Trunks vs Silver (I feel like I should be more confident in this happen, since on paper it has a lot of stuff going for it, but ... idk, I just don't think it'll happen next season)
Bradley vs Solidus (nothing really working against it, but nothing really pushing it ahead either)
Don't count on it:
ANY Saitama matchup (Ben's already said his piece on Saitama)
Any Sinestro matchup (not a super recognisable DC character to casuals and most of his matchups are just ... kinda there.
Any Guts matchup
Hit vs Sakuya (if it weren't for the Discord post this'd be in lol no)
K. Rool vs Blackbeard (if it hadn't lost it's initial steam, it'd be higher).
lol no:
Goku vs Superman 3 (If they use Goku, I feel like they're going to hold off until Super is finished. It's the same reason we haven't seen Luffy or Deku yet).