Actually, Dan and Wheelbarrow, I think you overstate the case. All of those who were removed from commands post 9/11 will be back in the LHS by May. There are actually very few people still to return from unpaid leave There will be approximately 30 new commands this year and, as we are now looking at a fleet of 60 aircraft by 2010 (Virgin press release last week), there should be in the region of 240-300 new commands between now and then. There won't be many retirements before that date, but after 2010 Virgin's pilot workforce will begin to show a similar age-related turnover to most airlines (though new legislation may delay that for all EU airlines).
While command at Virgin is never going to return to the <3 years it was in the early days (when even a single new aircraft would represent a huge percentage increase in commands), it is still likely to be faster than it is at BA and other mature airlines whose fleets are unlikely to expand greatly. I would guess that a sensible estimate is between 7 and 10 years until a command at Virgin at the moment.