I have a hard time believing Brendan's pledge to diversity given Mozilla's non-support for Gecko embedding.

There's a number of Gecko-based browsers, e.g. Camino, and they've left their users in the lurch by ending support for Gecko embedding: http://caminobrowser.org/blog/2011/#mozembedding

Mike Pinkerton has for years been voicing rightful criticism that Mozilla is focussing on Firefox and nothing else, see e.g. this interview of 2006: http://mozillamemory.org/detailview.php?id=7277

If Mozilla really wants diversity, why haven't they made an effort to make Gecko attractive for embedding, thus providing an alternative to WebKit? Instead they've done the exact opposite.