Here are some links:

One time swap out https://support.google.com/glass/answer/3501111#whats_change...

Google to let Glass owners swap out for a prescription-compatible version, invite three friends to buy Glass too http://www.glassgum.com/2013/10/28/google-to-let-glass-owner...

Google Glass Design Upgrade Revealed http://www.glassgum.com/2013/10/29/google-glass-design-upgra...

Google Glass Upgrade Arrives Just in Time for New Year’s http://www.glassgum.com/2013/12/16/google-glass-upgrade-arri...