We're cruising .82 to .84 these days; that's fast enough.
Not if you want to go say, London to Sydney. Long haul airlines advertising is primarily based on listing the on board facilities for passing the time. 'You won't get quite as bored on our flights as other peoples'. Rather as if telephone baning services competed on the basis of the music you had to liten to while on hold.
Once you can fly between the two major cities in the world which are furthest apart, do a few hours work, then get back the same day there will be no advantage in going faster. But that's a long way ahead.