When you look at Glock, as a gun maker, and compare them to other gun makers, one thing stands out...Glock was started with the purpose of building a military handgun and has always made guns that are very clearly for military, and then law enforcement, use. Fortunately for them, and for us, they made a product that also fit the civilian market well.
Their one variance was the G36. You could argue it was aimed at off duty use by police, and perhaps so, but compared to the rest of their line, as well as comparable pistols, it really hasn't been a big hit. Looking at it from that perspective, why would they make another slimline/single stack pistol? The one they made, despite being every bit as good as their other guns, has been out sold (it would seem) by the competition. It really doesn't make sense to put the time, money and effort into a gun that might flop, when they can build guns that they know will be sold.
The other gun makers, for the most part, were not started to build a military gun/have not continued to build only military/law enforcement guns.
As for the carbine, this is another rumor that's been out there in the ether forever. It, at least, makes sense, as it would have a military and law enforcement application.
Having just been at Glock two weeks ago, I can tell you there's a lot of construction going on. It's been in progress for several years now and there's still a long way to go.
I wouldn't hold my breath waiting for either product to come out. I wouldn't expect to hear about new products being launched until they were ready to ship, or at least ready to start production, as Glock is a company that holds such information close. Better to surprise the competition.