Considering that the Titan is extremely expensive, and is mostly a niche buy (Nvidia said it themselves) AMD does not need to worry about anything in the first place, considering that Nvidia wont be seeing anything special from the 700 series as well. Both 8k and 700 series have been told to be rebrands, so buying them is really not important, given that you can take a 7k series and hit the same performance on most 8k series cards. (probably)
Nvidia blew their load on the Titan, so neither company will be getting much this year. Its best to stick with the upper 7k series cards, and the 670 and 680 cards until a new architecture release is confirmed.