With the continued growth of Megabus, how much has National Express got left in its tank?

I've had to travel a few long distance journeys recently, and as the train was ridiculously expensive, I looked at coaches. Every journey I looked at, Megabus was cheaper and quicker than National 'Express' (Indeed, my Megabus into Edinburgh the other week overtook the National Express coach on the A1).

Further to that, in my opinion Megabus Astromegas and Elite interdecks give off a far more premium impression than the National Express standard Levante.