I'm sure Switch will get a lot of third party support but I'm unsure at the moment how sales are going to be for large games on cartridge that don't sell well in Japan. Smaller indie games mostly without retail releases I'm sure will be common as will conversions from android, ios etc based on mobile game engines. How many big third party releases come to Switch will be dictated by Switch owner's buying choices. If they prefer to buy games at a lower cost for more powerful hardware rather than have that game available to them port-ably then commercial support will reduce.
Personally I don't think US and European developer support is critical to Switch success, its more about Nintendo's own games and other Japanese developers so even if we see less big games on Switch its really nothing to worry about. It's good if it gets them though. It will be interesting to see how Doom and Skyrim fared worldwide after Christmas I'm not hopeful though. Both games deserve to do well but both games are incredibly cheap on other formats too. I suspect they will do better business as discounted download games sometime in the future.
I'm in the UK though and the Switch just like in most of Europe hasn't had the same success as Japan or US. It's really down to US consumers for the success of big US developed titles on Switch. It feels like Switch has a younger audience in Europe compared to US and Japan.
