We're cruising .82 to .84 these days; that's fast enough.
Going faster sounds great, but there's a much higher cost associated with the speed.
You can go as fast as you're willing to pay. If you want to well exceed the speed of sound, go rent a Mig in Russia for a ride; you can do it at high cost, but to what end?
Surely we can go faster, but to what end? I don't see the need, myself.