ok so heres what the S6 should have
Im assuming they'll use the galaxy alpha as a base for the phone's design
2.5 ghz snapdragon 810
3GB of RAM
5.3 inch screen with a 1080p screen super amoled display ( 2K SCREENS ARE OVERKILL!!!!, if they bump the screen res to 1920 x 1600 res NO MORE)
front facing speakers ( Samsung just buy one of Seinheiser or Audiotechnica and have them handle the Audio quality.)
USB 3.0 (sync and charging) support plus quick charge 2.0 + Oppo find 7 charging speeds
Stop trying to break off from Google, try making a near stock version of touchwiz, actually make a good version of touchwiz.
motion gestures for the phone like the M8 or the 1+1
32/64 GB of internal storage with micro SD card support up to 128 GB
3600 MAH battery (removable)
Scrap the fingerprint scanner, who actually uses it
On screen buttons ( time to conform Samung !!!)
get rid of S voice(wont happen but instead when you double tap the home screen you get google now.)
Improved low light preformance
Make it easier to Root.
Not all of them will be done of course but instead Samsung should cut down on the number of phones they release. release a mini version and the regular size version with the same specs.