IMHO, it's all about if P10 can hit 1440p60/4k30 in the titles one would expect it to (ex: similar to a OC 980 or stockish Nano/Fury Vanilla)...be it stock or overclocked. If it can do that, and is cheaper than anything else than can do it, it should be a good chip. IMHO over-all perf compared to 1070 doesn't matter, because what is another few fps that doesn't effect your v-sync? It's all about that 'vr-spec' (which is essentially slightly faster than a 980, or exactly where 'C7' is pinned), or more-or-less the normalized scaled spec between an xbox at 900p or ps4 at 1080p at max...essentially the 'base' clock of a 1070.
If that doesn't fit whichever pertinent criteria (to the buyer, be it avg or min framerate, stock/overclocked) than buy a 1070/980ti, which for all intents and purposes look to be incredibly, incredibly close. Yes, 980ti has 46.6% more units, and 1070 ~75% of the total allowable power usage, but is also on a process that is 2x more efficient with slightly less power consumed by RAM. When you take clockspeed potential of both 980ti and what we've seen from 1080 into account...it should be really close. A 980ti does what, ~1366 within it's stock power envelope?...which would be equal to around 2ghz on a 1070. Yes, both can/could potentially clock higher, but as a rule of thumb, you can see they're going to be pretty close (dependant on if 1070, with it's disabled units, can clock slightly higher than 1080 and/or nvidia gives the same max power target...and/or you mod you bios which is a whole 'nother can of worms).
For others, they will shell out massive money for a 1080, chasing that 4k60 dream (mostly in vain, judging by founder's edition results).
Everyone else will hold on to our wallets and pray the 4k60 Gods are kind when they eventually arrive, which feels like waiting for Godot.
Hopefully I've broken down the market in a more-or-less succinct way: We're still, for all intents and realistic purposes, at 1440p60/4k30. Yes, a card that performs slightly better may get you over the hump in SOME games. But, as a manner of generalization, 1080 won't get us there. 1070 MAY not get us further than an overclocked Polaris. This is why we should wait and see what happens over the next month or so.
Edit: (Apologies for the kind-of OT, It's in the spirit of giving thoughts relative to 980ti/1070.)