From the last RfC meeting on 13 August 2014:

21:46:05 <sumanah> mark: re https://www.mediawiki.org/wiki/Talk:Requests_for_comment/Standardized_thumbnails_sizes did you end up organizing the sprint you suggested?
21:46:21 <sumanah> "As you know there's a fair amount of desire to change the way thumb handling & storage works, support more variants (sizes, quality), etc by various teams. I'm starting to think it would be good for us to organise a sprint on this very topic, get the multimedia team, relevant Ops people and some other interested developers from other teams and really dive into these problems."

PS: not sure whether this Mark refers to Holmquist or Bergsma -- assuming the former.