From what I've been reading the new sources have just recently been able to compile properly over at Cyanogen and things are in the extremely early testing stage there. From what I've read Jelly Bean 4.3 is a major rework that takes advantage of today's modern phones with multi-core processors and better GPUs than we have. The posts I've seen state that many things are broken and that it will take a while before things like hardware acceleration work as expected. Think of the current state of development as early alpha. Give them 3-6 months and we'll probably be seeing the MOD stably ported to devices that need heavy modification. Before then you'll only see those that don't need much reworking.
Ours on the other hand is a different story. The HD2 is getting long in the tooth and there are fewer and fewer developers working on it. Just go to the other forum and see how dead it is over there compared to how it was just 6 months ago. Remember all of the hype about developing a viable working 3.x kernel for the HD2 on Ice Cream Sandwich? Well ICS came and went as have 2 major revisions of Jelly Bean and we've still yet to see a production quality kernel from them. Tytung's 2.6.32 kernel is still the best kernel for our devices, yet it's nearly the same one he developed for Gingerbread over two years ago.
I just wouldn't get my hopes up too high for 4.3.x that's all. I'm satisfied with 4.2.x and glad I can run just about anything I throw at it.
Current device: HTC Amaze 4G
Bootloader: HTC - Dev unlocked, S-on
Recovery: 4ext - smart flash enabled
ROM: CM-10 - Compiled and customized by me - thanks spostsstar89 - CM - Team Nightmare
Xposed framework - rovo89
GravityBox - C3C076
Previous device: HTC HD2 (TMOUS - LEO1024)
Final ROM: NexusHD2-JellyBean-CM10.1.3 v2.7 - Tytung
Had more lives than a cat, best handset I ever owned
Lesson: If it ain't broke, don't fix it!