Good question. All hardware gurus say the TI processor is the most open SoC of all, so easy to write any needed drivers. Really they should at least keep the GN current for 24 months, as that would at least keep it up to date the length of a typical carrier contract. Kit Kat is more efficient with system hardware, so no reason it wouldnt run great on GN. I think Google needs to do it.
There are already people releasing roms so that you can easily flash kitkat on there. I'm also pretty sure Cyanogenmod will release a rom for it...so basically there isn't really anything to worry about.
It's true that Cyanogenmod does a great job with ROMs, but they have a difficult time getting full functionality of all the device hardware. Why? because OEMs do not always release their drivers back to the AOSP, so Cyanogenmod (and anyone else for that matter) cannot always get certain hardware to fully function. For instance, Qualcomm (maker of the popular Snapdragon SoC) does not make their graphics software drivers available to Android Open Source Project. This practice by OEMs is why we can't always get all the functionality of devices from our devices through custom ROMs.
Already had the conversation with Google and Verizon. Verizon doesn't even have a 32GB MotoX yet, under the Moto Maker program. Morons, both of them. My Gnex bit the dust replaced it with a Droid Maxx 32GB for now. As soon as Project Ara releases production models, That's what I'll have. 18 months for a nexus device? Software is king not Hardware. XDA devs will keep it running. I even had Ubuntu Touch working on it. After this phone no more Verizon. Morons. There is a point release Verizon is sitting on for the Gnex, but not 4.4. Whether and when they release it is anyone's guess. Everyone I know hates Verizon, for good reason. I don't think big red will ever see another nexus device again. ever. one giant charlie foxtrot.
Google says Galaxy Nexus won't get it but I have upgraded to Nexus 5.