And then Letterman would later be replaced by game shows... Las Vegas Gambit and Blockbusters. On Letterman's final show, there was a musical number about them being replaced by Las Vegas Gambit, with a "living deck" of cards. (Originally in the bonus game, members of the audience wearing cards like sandwich boards were in the audience, with the same premise of getting 21 without going over. This was likely the pilot only and the idea was scrapped when it became a series)
Let's say that Wheel DID get the axe... do you think Merv would've tried to syndicate the show with Chuck hosting? Chain Reaction, honestly, while an entertaining enough game to watch, doesn't quite have the same appeal as Wheel does, so I think Chain Reaction would've been cancelled maybe a year or so later.