Interesting. The BajaNomad Forum has lots of info and some pics on it. http://forums.bajanomad.com/viewthread.php?tid=77208 I haven't read the whole thing yet, but hopefully it gets done by February or March. I still haven't decided on whether or not I want to drive to Cabo San Lucas or do a loop in Chihuahua and Coahuila (Reynosa - Ojinaga). MX 5 would definitely be a very useful shortcut once complete, should I drive to Cabo San Lucas. If anyone knows anything new, I would love to hear about it.
Looks like they're paving more of it. The designation currently follows a dirt road to MX 1, so it's not really an extension of the route itself.