MH5 is likely going to be the actual cross-gen release, rather than MHX. Unless they do MHX(G) and, potentially, MH:Stories NX (as I have been dubious of for a long time) for next year, and we see MH5 in 2017 with no cross-gen. But I doubt it. The MH fanbase on the 3DS is far too enormous to skip over in 2016 with a mainline release, and they can do as they did with 3DS to N3DS and give the NX variant an enormous texture (and even a model) bump. (Honestly, I don't even foresee a MHXG but a MHX-DLC release, as I think Capcom is more into trying to service their games going forward than just keep releasing new disc packages. The fatigue on that is, also, showing with the drops in MH4 -> MH4G where many players just didn't feel the desire to rebuy the bulk of the same game.)
But the mention of it now feels like its more aimed at the 3DS <-> NX transition than the already existing-but-passing PS3/PS4 transition (by next year the PS3 active and healthy base will be extremely diminished, but the 3DS one will likely still be fairly active given its... 20+ million body count). Potentially, this also refers to cross-gen Vita -> NX for the handheld side of things getting eaten up by the only handheld left on the market. 2016 to 2017 is way too late for the PS3, and will be running into EoR for the Vita from a tech/toolchain perspective.