This is an odd year where Nintendo can go either way on big announcements. On one hand, they've got to do a blowout on Pokemon, Animal Crossing, and Luigi's Mansion. Between those three, they could easily knock out 25 minutes.
My guess is that this E3 mostly focuses on this year and the first half of 2020. So I'll go with two mid-tier announcements for next year and the announcement of another partnership with a 3rd party for one more big game.