Never. I'll wait until there's a credible rumor that says it's coming. I don't think it's out of the question but I have very, very low expectations for it happening given LA Noire didn't chart in the top 20 NPD or top 10 Switch games for November.
Rockstar will probably invest their time and resources into finishing RDR 2 and making online content for it and GTA V.
they just need to not make it a simple port but add something, ANYTHING, any cosmetic DLC will do.... and they can secure a couple million on the switch version.
huge ass open world games are at home on the switch, you can play them anywhere and turn them off anywhere. that alone would make it the best version ever
I'm too used to it on PS4 to go back to playing it in PS3 quality tbh. I don't think it's going to happen either, but the Switch is not powerful enough to do it justice.