I'm fully expecting both MS and Sony to bring new consoles in either holiday 17 or 18, and this has been my belief since current gen was launched.
Future updates will be dictated by hardware advancements and increasing demand for more power for things like VR and 4K. There won't be a set time schedule for upgrades, they'll come when there's enough hardware updates to warrant an upgraded SKU. These days it'll invariably mean at least three years, expecting at least one process node jump. 4-5 years is more likely in my opinion.
7 year console generations never even existed outside PS360 which were back during launch top of the line hardware sold at a loss, and needed a long time recuperate the losses. With a consistent x86 mainstream approach with forwards/backwards compatibility console gamers can keep playing their games, Sony and MS can expect hardware sold in the black, and devs can expect a larger user base for games supporting the newest hardware, instead of the old risky and expensive clean sweep between generations.
The only negatives I see worth mentioning is devs would need to optimize for two SKUs, which isn't really a big problem considering what they're doing now with remasters and PC ports. Given the transition period between the new and old SKU, devs might keep making games for the lowest common denominator, and the only benefits of the new SKU might be higher res and FPS. I'd still expect them to eventually start making games with only the newest SKU in mind, which could in turn create problems if they try to shoehorn poorly working versions for the older consoles. Ultimately it's not really any different from what has been already done with the recent transition, except we had no real compatibility and everything has been done extremely expensively manually porting everything between the old and new consoles. The rest of the complaints I see as nothing but fearing change, missing out, and feeling bad when their relatively recent console gets dethroned in favor of a newer model.
As for 4K gaming, It's just marketing talk meant for people who don't know anything about technology and need simple buzzwords. I don't think you're going to be playing AAA titles at 4K on a console in a few years, that's just not a priority for developers outside marketing for idiots. Resolution simply isn't the best way to bring better visuals in games at this point. Most console gamers are stuck with 1080p TV's for years, so more than likely devs will keep 1080p as the resolution, and utilize the extra power for things like supersampling /AA/HDR and more advanced effects. There's still going to be 4K games no doubt, but those are likely to be limited to otherwise undemanding games.
