Nah, it ain't happening. If we're getting a PS5 in 2018-2019 (which is likely) then they're not going to put out an upgraded PS4 that'll be outdated in a year or two.
This.
Thank you.
PS5 in 2018 or 2019 but cross-gen games would go on a lot longer next time. PS4 would not die a year or two after PS5's arrival. PS4 would continue to be sold and supported for years after as a low-cost entry level console. Much cheaper to manufacture than PS3 Slim and Super Slim.
Sony will need and want another source of revenue with Vita gone. There won't be another Sony handheld, but they'd be more than happy to sell you PS4s and PS5s for many years to come. Along with PlayStationVR and PSN subscriptions. And of course, games, both physical and digital, though PS5 certainly won't be digital only.
Yeah, don't expect a new, upgraded PS4.