Assuming we’re in the very early stages of a housing recovery (and that’s not guaranteed at this point), the last to rebound will be new luxury condos that are largely sitting unsold these days in Boston. When will they start to move? When you see a sustainable change in the stock market. Not before. The Dow has recovered a bit of ground in recent months, but not nearly enough to recoup last year’s losses and to spark a lot of high-end sales.