I think that it would be a clever idea to use the WiiU version and build upon it. You can add new tracks on MK8 Switch, and new modes, weapons, maps in Splatoon, and focus on another franchises. I mean, let's be honest, it's not like MK games are reinventing the wheel, so I'd be cool with it. And I'd buy it again if it comes with 20 or more new tracks, for sure.

Perhaps, but at this point we have no idea what else is being developed and planned for 2017.

3D Mario was briefly shown, Retro has been developing their new game for close to 3 years, Next Level is rumored to be working on Luigi's Mansion 3, etc.

Mario Kart final mix(?)

Depends how many games it launches with doesn't it. So far we have one confirmed and two rumoured. 

Yeah I mean really that's why Nintendo takes forever making games because they don't really use there old assets. But when they do look at the differance. MM game out like 1.5 years after OoT with same engine. Now they have HD engines for MK, Splat , Zelda, DKTF etc we should see much faster sequels

Add a decent battle mode and I might get MK8 a second time. 

Well most if not all remasters already run in a higher resolution. So.I don't think that therm applies very well.

Splatoon 1.5, Mario Kart 8.5, Smash Bros. U 1.5 ... bring it on I guess.

I think Splatoon will be very early in the Switch lifecycle (maybe even day 1), Nintendo is going to want that because it showed system selling ability in Japan even beyond what Mario Kart and Smash did, the Wii U was just so anemic that Nintendo had to kill it, but they will want Splatoon back quick.

I wonder if mario kart will be bundled with the console. Then being a port to switch won't be too big a deal. However if not then it really needs to be upgraded to make use of the greater gpu, cpu power and the extra memory. Moving the engine from ppc to arm code surely means an upgrade here or there in that process.

You have to remember people expect poor underpowered hardware from Nintendo nowadays. If they release a game at launch that looks pretty much the same as the wii u version people will assume the worst about the hardware.

Nintendo need to impress with their games which is much easier to do with cartoon graphics so if the Switch is about 3x wii u performance it needs to show it.

New content and better visuals, something similar will be for Smash Bros 4 port also.