People we should all temper our expectations about the next gen, so far we always had the luxury of a new process node, but not now. NV die size is pretty much maxed out, AMD can increase it by some 30%. We won't have gains like GF100 to GK100 or Cayman to Hawaii. Even those gains were interrupted by pseudo high-end cards with GK104 with its 256bit interface being the biggest culprit. The time were we got double the performance went by with the release of tahiti and then GK104. We are being milked. Performance gains will be tiered, no more 2x jumps in performance. For something with a performace close to contemporary cards in SLI/CF we have to wait for 20nm. But we can have such performance now for even lower price by buying 2xR290. This card offers phenomal performance for the price. I can bet that its performance per euro won't be beaten for quite some time yet, especially with the price per transistor rising slightly with 20nm. Prepare for another mediocre performance increase akin to 580 to 680. For true flagship we will have to wait at least 6-9 months for a Titan edition and another 3 months for gamer card that won't fleece the consumer wholly just partly. AMD should counter that real flagship card from NV in a few months, I just hope that they won't repeat their mistake and design a decent reference cooler for once so we won't have to wait another few months for aftermarket design to get the true next gen perf in a single card for a price that can be swallowed, I still think that 2x290 is a great deal and due to the transistor cost not decreasing with smaller nodes will remain a great choice from price performance perspective. I think that even the flagship 20nm Maxwell will just match 2x290 for more money and all of that a year later at the least. 70%-100% jumps in performance with new generations are behind us, sadly. People can argue that that's not the case till they are blue in the face but that's the truth. We will get tiered increases in performance on the order of 30-40%, just enough to compel enthusiast to upgrade and the users of older cards.
UPDATE:
Some people champion Maxwell on the merits of it offering 2x performance per watt but what matters for absolute performance is performance per mm2. How much better is it in that metric? That's what improvement we will see in pure performance. I don't care about perf per watt aside from mobile but in desktops? no way. What's important to me is how that heat is removed which AMD had and epic failure with its reference r290 cards I didn't buy that 1.2KW PSU for nothing. If idle power is low then 2-3 hours of gaming won't make a dent in power bill. 600W for power efficient 20nm maxwell or 1100W for 3x r290 with better perf. the choice is clear to me. unfortunately I will have to change the platform where I can install three cards with a slot of space between 3 of them. I won't play for more 3 hours a day, more like 1h on average. Power consumption saving is inconsequential.