Found an interesting article by someone who actually seems to know a little bit about the new Glock pistol that is supposed to launch next year.
LINK: Gen 4 Glock: A Look at the New Features :: Guns Holsters and Gear
Here is the Cliffs Notes version:
New frame designed around the .40 caliber to address feed reliability issues that surface when weapon-mounted lights are attached to the Model 22 & 23.
Ambidextrous slide stop lever.
A more aggressive bevel on the magazine well.
Reversible magazine release catch.
No pressing the trigger to field strip.
A grip texture somewhere between the GEN3 grip and the new RTF frames. Reportedly the RTF frames were produced largely as an experiment, and the consensus seems to be that they are a little to rough for a carry gun.
Improved factory sights, including a "straight-8" style sight like those produced by Heinie.
What you likely WILL NOT see on the GEN4 Glock:
Magazine disconnect safety.
External safety lever.
Ambidextrous magazine release (button on both sides rather than interchangeable).
Slide serrations forward of the ejection port.