It definitely takes time to port games over. I think this delay factor is going to surprise people on both Third Party support and the Switch's performance as a console. For 2018 I expect most Third Party games to be ports, mostly old games ported over, but a few games with simultaneous releases on all consoles like Dark Souls. For 2019, I expect lots of simultaneous releases and even a notable number of Switch exclusives from Third Parties. Then in 2010+ the number of Third Party of exclusives is going to grow and grow.
The Switch is currently a large snowball rolling down hill. In a few years it will be an avalanche of great games.