This margin will only increase with time as Apple has far more resources to pour into R&D, production, etc than any other company. The fact that they are ahead or at the worst, slightly behind now, bodes well for them in the near future.
5 years from now, will there be any desktops that can rival them? Now.... if only they ran Windows natively
They will have the performance per watt crown for at least 3 years, if not more, but Intel is supposedly putting huge effort into Arrowlake to compete against the Mx series. I hope AMD also takes this more seriously with Zen 5 onward. At this stage my next laptop might be Apple if the M2 series show nice uplifts. An M2 max would be pretty tempting.
I wish Apple weren't so insular and sold their cpu's to third parties and as you say they could run windows or even Linux.