Neither Sony nor MS would follow Ninty in a 2016 launch, and if that console must replace both 3DS and Wii U, 2016 is too early for Ninty too, even more so considering that Ninty never rushes HW development, to avoid having to accept compromises on quality.
It will be 2017 or 2018 for Ninty and 2018 or 2019 for Sony and MS. Some form of unified home-portable design could be adopted by Sony and MS too, as mobile gaming will have overwhelmed standalone portables too much by then.