Understand the revolutionary air conditioning system in the 787 has found to be somewhat problematic and requires a substantial redesign. Throw on another couple of years delays and with the A350 possibly flying in 2013 it will be close. I suppose they could always deliver the first bunch unpressurised.
Of course the 747-8 will be on schedule, it's just a couple of plugs and a pair of winglets, how hard can that be?