silverforce should just skip this generation
This isn't a bad idea actually. There aren't many great options for 4K monitors, nevermind FreeSync/GSync 4K monitors. I can't imagine buying a $1K 4K monitor without either of those features because 4K brings the pain to modern GPUs and adaptive sync really helps in the 30-60 fps range. The other thing is if someone is skipping GW titles until they hit bargain prices, R9 290X CF still plays vendor agnostic titles very well. Therefore, I don't think he has an urgent need to upgrade. Also, I do believe that 14nm/16nm + new architectures + HBM2 will provide a bigger boost in performance than this generation will. Since HD7970/R9 200 series have depreciated so much at this point, it's not as if selling those cards now is strategic anymore -- that point is long gone.
Financially holding on to R9 290/290X CF is actually worthwhile. Here is why:
Let's say you can resell a 290X used for $240 today, or $480 for both, in 18-24 months, you'll probably be able to resell them for $120-130 each, or $240-260 for both, which means a loss of resale value of $120-130 per 1 card.
However, if you buy a $600-800 28nm card today such as GM200, that card will likely lose $200-300 in value in 24 months. Upgrade to 2 of those and you are looking to lose $400-600 in resale value because 14nm/16nm GPUs will level this gen's flagships as far as price/performance goes - you can count on it (i.e., recall $330 970 ~ $700 780Ti just 10 months from launch. OUCH). Therefore, if money is a factor, if someone missed the 'perfect' time to resell his/her old card, it isn't such a bad idea to skip a generation(s) if a gamer is OK turning down some settings and doesn't need to run everything on Ultra in every game.