Sometimes, change is good. But for something as entrenched as fundamental Perl regular expression syntax, that change has to be really good.
Even if we were inventing regular expressions in a vacuum with no existing code out there (which we most certainly are not. I wonder what point size it would take to stretch all of the capture brackets in current production code, end-to-end, to the moon...), I'm not convinced. I type (?:) a lot less often than I type (), so I believe the shorter code should support the more common case, as has been a long-standing design tenet of Perl.