GTX 780 Ti Vs GTX 970 (4K)

So I'm going to be upgrading my setup. What would be best for 4K (Single monitor)?

R9 290X 8GB or wait for the 8 GB GTX970/980 to drop the extra vram is useful for 4k gaming.

R9 290X 8GB. It beats the new nvidia cards in 4k. 
http://www.newegg.com/Product/Product.aspx?Item=N82E16814202129&cm_re=8gb_290x-_-14-202-129-_-Product 

Whichever you choose, buy two.

just buy a 980 - a single 980 is fine for 4k - i know because i own two.  One was plenty for 4k without AA.  two lets you have all the eye candy.

Or buy 1 or 2 290x's