If they could somehow do both it would make absolute sense to launch with both. That would make it possibly the strongest launch ever for a Nintendo system.
I'm not sure if it would be possible but if Nintendo are combining their development on to Switch doesn't that mean there's a ton of 3DS teams who might have projects ready?
EDIT: Zelda could compete with Skyrim but it might also have the opposite effect. People will buy Switch for Zelda and possibly pick up Skyrim because they want another game at launch.
That is a good question. Nothing really focuses on this aspect, so that either means that 3ds is still held up as its own pillar (at least for the moment, who knows how it'll be later on) or that we happen to not have any journalists with sources in the know about those developers (which would be a strange coincidence). Nor do have any rumours about 3ds ports coming over to the Switch, while the WiiU ports are abundant. There are some reasons for that, which we have discussed at length, but you would expect at least some handheld devs from Nintendo to take a look at the Switch (and we know Pokémon will likely come, so why not other games?).