Nintendo often publishes Capcom's games for their systems outside of Japan.... so who knows maybe Nintendo will be the ones who announce it in a bit... Graphically it didn't really look insane in the trailer (Monster Hunter World) so I don't see why the Switch would be out of the question...
bear in mind Nintendo actually announced TWO games exclusively in the Tree House demos today (Mario + Luigi remake and Metroid II remake) so it's possible (and somewhat likely) that they announce something else in the next few days of Treehouse (I think E3's last day is Thursday)
if Capcom refuses to release Monster Hunter games on Nintendo systems in the West that'll just be silly, they have a strong fanbase there on Nintendo systems, even if it's not near the levels of the Japanese fanbase (which nothing will match regardless of platform)