All 6 original Five Nights at Freddy's games are going to make their way to Switch. This information comes straight from the creator himself.
I’m working closely with the people at Clickteam to create new, improved, HD ports of all of the original games! They will be released on Android, iOS, Switch, XBox and PlayStation!
It seems like this might take some time, but hopefully the package sees release before 2019 closes out. When there's more info on upgrades and a release date, we'll bring that to you.