I hope there will not be that many multi platform titles / ports. Now before you get pissed let me explain.
Nintendo has always been a different experience from other consoles. PS4 and Xbox One are almost identical, they offer the same experiences. Of course there are exclusives and people prefer Live over Plus, but mostly it's the same. PS4 now has VR support, but that's at the price of a new console.
If the Switch is identical to the PS4 and Xbox One there is no reason for it to exist in a market where a lot of people already own PS4s and Xbox Ones. Would you really buy a Switch if it's the same experience as a PS4 but with less power? It's not fair to think the Switch will have the same power as a PS4 or Xbox One, if it does it would be phenomenal.
Launching the same games on PS4/Xbox One and the Switch will result in comparison. The Switch version will always look the worst out of the 3. Think back to Assassin's Creed 3 and Black Flag on Wii U, where people complained it looked worst than the PS3 and Xbox 360 versions of the game. The release of even more powerful hardware by Sony and Microsoft will push this even further.
Sony and Microsoft are also miles ahead with their online experiences, another reason why a game might be better on PS4 or Xbox One.
These are all reasons why ports/multi platform titles might be a bad idea, even if they could port their game with the push of a button (which it will not).
Third party support is good for the system and us gamers, but I hope these companies will create different experiences and games for the Switch and not lesser ports of PS4/Xbox One games. Unless of course it's an indie game like Don't Starve or Cuphead, games that not look worse on the Switch.