I think they're just hoping future directs and E3 have more games for 2016-2017.
OT: I'd be very surprised if Wii U's sucessor comes out next year. Nintendo has made no move to make the Wii U significantly cheaper than its launch price of 350$ (and the 300$ price was an option at launch too). This shows that Nintendo has no intention of being competitive for market share. And with the lack of high quality mainstream games this recent holiday season, its safe to predict Nintendo has moved on from making big games on the Wii U and are moving on to its successor. Whether or not if this is a dumb move since Wii U life span is less than 5 years is not the main issue. The main issue is Nintendo has shown they are ready to move on.
People may be expecting something at E3 for late 2016 and 2017 but consider this.
in 2013: Xenoblade X and FE was announced. Only one of those game has come out to the Western market.
In 2014: Zelda U and Star Fox Zero were announced and shown: None of these games have been released yet
In 2015: The only new games shown were Animal Crossing and Mario Tennis which have already released.
Additionally, all 2016 games have been announced or shown before 2015 (Pokken was hinted a year after X with a footage of Blazekin and Lucario)
Based on this trend, if Nintendo has any games for 2017, they would have shown it by now to give us something to hold onto. 2015 did not give us anything new for 2016 let alone 2017.
Actually Zelda U is announced in same legendary Nintendo Direct with Xenoblade X, FE and Yoshi Woolly World in January 2013.
Saying that, we didnt had single one new announcement that isn't small project, port or spin off basically from E3 2014.