Would violate the laws of physics but yeah.

.40 cal carbine...bullpup?

Pistol with sigbrace?  

10 mil g41

A better grip. That's all.

They do not need to change. They will never drastically change their style or platform.

With that being said, single stack 9mm is next. They have to. How small can they make it? That's still up for discussion. But it will happen

Glocks sell well as they are.  They have some flaws, but overall it's a tough design to beat as it is. Massive design changes or New/risky designs can ruin a company...just ask remmy about the r51 if you don't beleive me. Hell, ask glock how well the g4 was received and that will answer a lot of questions as to why glock hasn't done anything radically new in some time.

That being said, front slide serrations would be welcome, improved sights from the factory would be welcome (narrow front post, wide rear notch)  a contoured grip, with texturing similar to stippling (while maintaining the same grip angle) would be welcome. Stronger ejection (I want to see brass fly like it does out of a cz) would be welcome.

I'd also love to have the trigger safety sit flush with the trigger face when depressed.