I just noticed this:

"edit 11/27/2015: demo version of RingCT using the MLSAG's is coded - next up is implementing 1. Diffie helman passing of masks and 2. implement a short representation of amounts"

https://www.reddit.com/r/Monero/comments/3pw30d/ringct_for_monero_updated_versions/

Progress seems to be happening pretty quickly! After the next implementation step it sounds like the proof of concept should be pretty well established.  It seems to be that RingCT is a matter of WHEN instead of IF.