The way I see this, sony should stick to its guns here.
I find it hard to see a next-gen or half-next-gen console succeeding next year. Consumers have just purchased their new consoles, and devs have just gotten started, no one is terribly eager to start this all over again. Specially if it is gonna be another slow start diminished-returns start like this one (I think it would be actually worse, both for being too early chronologically and for 1.8-6Tf being an even smaller leap)
If MS really releases a 5Tf console next year, it will still be a xbone 1.5 ms like it or not. It will be big and expensive, and starting from scratch with zero user-base. Devs just won't bother. They will brute-force whatever easier changes they can (increase frame rates and res) and call it a day. Thats enough to win digital foundry comparisons, not enough to sell tens of millions if consoles in my oppinion.
PS4k is in the same position really, bit if the rummors and speciation are true, it will cost about as much as a ps4 to manufacture, all componets can stay the same aside from the main apu, and even that can be used for vanilla ps4 units when deffective. Its would be such a huge economical win for sony. They could sell with a larger margin, and still be cheaper than xbox two, all while staying with a small quiet and ellegant machine.
I never thought they would sell it much like a better gfx machine. With a 2x differential, realistically we are talking about less fps dips, and a mild resolution-improvement + a 4k upscale. If they keep it like that, they don't really even enter the mad power competition against one two. Its just a "regular" ps4 that outputs at 4k, versus the diminishing returns expensive bulky 1.5 next-gen-wannabe beast.
The way I (a layman) see this market, gives me the feels such a battle is won by sony before it even starts.
Xbone Two would only confirm the narative that the One was underpowered and the impression that MS doesn't now what they are doing, and its high price will further cement xbox brand as niche. By the time the thing can start getting traction, sony can dreamcast it when a more substantial technological leap is feasible at an affordable price.