Splatoon was a mega hit but the second one seems to be more of the same where Super Mario Odyssey looks like a more original and appealing mario, something that will sell much better then the last entry.
I expect Splatoon to do good and Mario to do amazing. I also think the switch will be lowered in price around the time Mario releases, giving it more room to do well especially if its bundled in with the console.
Mario will outsell splatoon 2 to 1
Twitter @CyberMalistix