The Switch is still sold out and MK8D comes out in two weeks. So the Switch will likely still be sold out from launch/Zelda momentum when MK8D releases. Even though MK8D likely won't have the same hype as a MK9 it's still a mario kart so it is still a system seller, especially considering how few people bought Wii U. Switch will probably still be hard to find until June, at which point I expect people will be able to start finding it on a normal basis but sales should still be strong as Arms and Splatoon are released.
Launch strength for MK8D depends on how many of Switch early adopters are Wii U owners. If a majority of early adopters are Wii U owners then MK8D might not get off to a great start but should have huge legs as the switch should should eventually sell many tens of millions more than the Wii U did.
Either way, Minecraft is a big game and Street Fighter is a good non major release for May as well, and launch periods are always sparse, you can't expect a system seller every month, hell you can't expect that at any point in a system's lifetime. Switch is sold out, switch will continue to sell really well through the spring.







