Both 3DS and Wii U have a pretty solid/stacked release lineup for 2016, and Nintendo have gone on record stating they are in no hurry to replace the 3DS, as it's still selling well.
These threads really don't bring much new in terms of conversation. Nintendo would be unwise to rush NX out the door, they should make sure they have a strong and steady release lineup that will last far BEYOND launch, and thus NOT launch until 2016.
But I mean Wii U in 2016 will have: TP HD, Star Fox, SMT x FE, Mario & Sonic 2016 (meh but still), Pokken Tournament, very possibly Pikmin 4, and Zelda U.
And 3DS? In 2016 it'll get: Bravely Second, Hyrule Warriors Legends, Project X Zone 2, Final Fantasy Explorers, Fire Emblem Fates, Metroid Prime: Federation Force, DQVIII AND DQVIII ports, Sonic Boom: Fire & Ice (meh, but still), possibly Dragon Quest XI in NA, possibly Shin Megami Tensai IV: Final in NA, probably Monster Hunter X in NA, not to mention another Professor Layton game is in development.
So there's plenty coming down the pipeline over the next year for 3DS, and even Wii U has enough big releases to make 2016 a solid year, before we more than likely see an NX launch perhaps in the early half of 2017.