I say this so often, but never in a million years did I dream that Sega would not only exit the console business, but partner up directly with Nintendo for decades to come.
Mario and Sonic were so unilaterally ubiquitous with "video games" that you could hardly imagine them sharing the same room, much less working together hand-in-hand. It was a partnership that required cooperation on both sides of the table, but has sustained itself for a long while. Their union is perhaps best illustrated through the Mario & Sonic at the Olympic Games series, which has been pumping out steady releases since 2007.
The Olympic experiment has always been a sort of awkward cousin to the more striking Super Mario Party franchise, but Sega has a secret weapon up its sleeve this year: nostalgia!