Not a big fan of Cyanogen Inc and their ROMs, but I'm pretty hopeful that Paranoid Android will bring the update to the Galaxy Nexus
You can be pretty sure most of the major custom ROMs will continue to support the Galaxy Nexus for the foreseeable future. CM, PA, AOKP, Omni etc. And there'll probably be (unofficial) stock AOSP builds as well.
EDIT: There are already builds out there: http://forum.xda-developers.com/showthread.php?t=2507846 - has bugs which make it unsuitable for actual use at this point, but considering the amount of time 4.4 source has been available, you can be confident there'll be a decently usable ROM within a week or two.
EDIT: A few comments on the actual Android 4.4 release though; looks like they're removing almost everything from AOSP and making things closed source. For example, the launcher is now just a sort of "dummy" app, with all the actual content/functionality provided by the (closed source) Google Search app. (Almost?) all "Google" apps (which in many cases have replaced the AOSP apps; e.g. Google Music replaced AOSP Music a while back, AOSP Calender has been replaced by Google Calender, Hangouts replacing AOSP SMS app etc.) are closed source, and require the manufacture to be "licensed" or "partnered" or whatever term they use for it.
This isn't necessarily all bad though; Google apps get updated via Google Play, and thus OS updates become less and less necessary for getting the latest features as more and more of the OS is "relegated" to closed source, Play store updateable apps. Which obviously helps prevent fragmentation and provides a more unified experience across devices. It remains to be seen the extent to which this is effective though.
However, it does obviously go against the much talked about "openness" of Android and it's a hindrance to the various custom ROM teams trying to innovate in the Android space.
