> I should note that I’ve made a personal decision to scale back some other aspects of my professional life. I’m no longer accepting any new speaking engagements...

It is very hard to leave/scale-back unfinished business or commitments but it is a very important step before starting something new and big. I know many creative people who have tons of projects and commitments that they can't bring themselves to leave and as a result, they never have enough time to concentrate fully on their next big things. I highly commend John for making the tough decision of leaving Mozilla and lots of personal projects so that he could do something big.