I would have bet 5 btc you would not release it until July or August.
I don't know. The smart thing to do in my opinion would be as soon as possible if it is more power efficient than the S5. The sooner the better. Waiting longer only shortens the sell life span of the S6 similar to the S4. If the S6 has a built in PSU like the S4, with similar efficiency to the S5, it would behove them to release the S6 ASAP. If the S6 has "much" better efficiency than the S5 [Like .40 watts or lower], it would be best for them to wait for more S5's to be sold before releasing the S6.