Just not the current 28–135 non-L.
FWIW (which isn't much, granted), about a year ago Canon patented
updated designs for the 28-135 and 28-300. If/when FF bodies get down into the $1200 range, I bet we'll see an updated (non-L) 28-135 as an inexpensive kit lens (keeping the kit price under $1500), just as the current 28-135 was the kit lens for the last 'consumer FF bodies'.
Speaking for myself, I likely wouldn't be happy with the IQ of an EF non-L 24/28-xxx superzoom, and I think an L version of one would be fine optically, but not much smaller/lighter than the current 28-300 (which I don't mind carrying). I'd take a similarly-sized 24-250L over the 28-300L - that 4mm on the wide end makes a difference.