In the end it's not that CPU's hash way faster than GPU's at high N's; specifically, it's that CPU's cost less Watts per Kh/s to mine at higher N's.
Some examples of hash rates and setups with CPU's and GPUs @ N = 14; can be seen here -
http://yacoinwiki.tk/index.php/Mining_Hardware_ComparisonYou can see, as an example here @ N14
2x E5645 Procesors 2x 80W -- 1.53Kh/s
7950 GPU (250w) 1.3-1.5 Kh/s
Question is when is "the end" ?
For N=14 from your link :
R7 250 2 GB 32W 2.47 kH/s
Previous 7950 test was run with an old cgminer and/or unoptimized settings (lookup gap = 2 ...)
N=15 is nearly 10 months from here so the end will wait
