The prospect that the market gets flooded with 2nd hand 1070 and 1080 en masse, means that they should be either cheap enough to be competitive with that,or have a huge bump in power. If you have thousands of 1080 at sub 300$ On ebay, that makes a "2070", that is not a lot more powerful,a hard sell at 400-500$. The whole cryptocunrency bubble makes them compete with themselves,IF it bursts or if far better cards (perf/watt) come out and make the current gen obsolete in terms of mining.
GTX 1080 Ti =! GTX 1080. GTX 1080 is already a hard sell @ $500. (Speaking purely from a gaming performance perspective). Especially when compared to say, GTX 1070/1070 Ti. GTX 1080 Ti exists in a completely different ballpark of performance. We're talking upwards of 35% performance differential here. Why? Well, GTX 1080 is fully enabled GP104 (With the GTX 1070 being cutdown GP104). The 1080 Ti is the most cutdown variant of GP102. GP102 goes by another name; Titan X/XP/Quadro P6000. The latter of which costs over $5,000.
Point being? 1080 Ti aren't exactly "cheap" for Nvidia to manufacture. Rather, they're simply Quadros
that couldn't quite make the cut. So, instead of throwing these defective chips away, they repurpose them for their GeForce line. Problem is, Nvidia stopped production of GP102 quite a while ago. The amount of leftover chips is finite.
That's where "GTX 2070/2080" comes in. Cheaper to
manufacture, while offering similar performance to a 1080 Ti. Additionally, the "xx80/xx70/Ti" designation are 100% arbitrary and up in the air until the very last second. Mostly just marketing. Nobody, not even Nvidia, knows what it'll end up costing. That gets finalized much much closer to release.
