Maybe, maybe not. The way I see it, nvidia has an excellent architecture on their hands with Maxwell and while the truly halo part might need 20nm for sheer transistor count - it is also very possible that NV may scale Maxwell up a tad for more desktop GPUs.
Remember, NV's 60W TDP maxwell is twice the performance of the 65W Kepler or 65W Bonaire (I think, R7-250). So if they scale that up to maybe.....120W TDP, 150W TDP, they could still be well in the 28nm transistor window and have an appreciable performance gain over Kepler still.
I dunno. I just have a difficult time accept that NV will just go all year without releasing a new product especially when they have a capable new uarch on their hands; certainly 20nm is a constraining factor but that doesn't mean gains aren't still possible on 28nm. Now like I said, the true halo part may be 20nm if the delay IS true. We don't know, I sure hope not. I would like new products in tandem with the new intel platform, even if it arrives a few months or a quarter after.
Haswell-E sounds pretty tempting, or even Haswell refresh if the overclocking rumors are true.
In conjunction with a new GPU?
Should be a cool full system upgrade. But I don't know, i'm just speculating here. I'm hoping it happens whether 28nm mid range Maxwell or 20nm high end. I want new toys, basically.
But we'll see.