So Cathay are returning to Lgw from September 2016, 4 times a week with the A350.
HKG is a big market so it's a sure bet that LGW will have enough local demand to support a service. That still makes it 5 x 777's from LHR daily versus 0.6 x 350's daily (and that's just Cathay), although we should reasonably expect LGW to work up to a daily service in time.
This does not prove that Gatwick is the answer to the London problem.