UPDATE - The video call issue "somewhat" resolved...

I was just as frustrated with Google as everyone else when the 'Hangout' feature for Glass was removed back in May/June 2014. However, the concept of immersive applications for businesses of all kinds still persists, and not just in pure science. For example, the Remedy application for Glass, being piloted by Harvard and other Med Schools:

http://techcrunch.com/2014/08/25/remedy/

Remedy is essentially a virtual patient visit, aided by Glass, mobile devices, and interfaces to patient records. Indeed the medical industry stands to benefit immensely from this kind of revolution in handling patient treatment.

However, a true replacement for Hangout this is not, and a replacement for Hangout in general doesn't seem to be on the radar right now. HOWEVER, there is the Livestream app for Glass.

Livestream allows a Glass wearer to broadcast audio and video over glass to a web audience. The audience in turn can write text back to the Glass wearer, which shows up in the Glass app. In theory, this is pretty awesome. I have yet to experience the service without some hiccups in performance, however. For example, significant latency of the feed (ok, blame networks) but also complete dropping of the connection intermittently. I will continue to play with Livestream, but I'm hoping to find a better classroom app for Glass out there.