I feel pretty confident that Nvidia will have a card up their sleeve. I am taking nothing away from the 290X and truly believe at this price, it is a great card but Nvidia have always liked top dog spot....
If they released a full fat Titan, it would only perform about 5% faster than the Titan because it wouldn't be able to clock so high because of the heat. This also shows with the 780 Vs the Titan. The 780 can clock higher than a Titan and Classy 780's can hit 1400Mhz+ on air.
I am going to do a fanboy bit now as well.... For months and months, I heard that the 7970 was faster than the 680 because it overclocks much higher and the same with the 770. 50/50 in games but people posted that the 7970 was under clocked and would clock much higher and leave the 770 standing.
The 290X is a great card but can it beat an Overclocked 780/Titan? We will have to see