Absolutely! Even current sizing makes little sense. The typical difference in length from a Small to XXL is about 10 cm, despite the recommended rider size changing by over 30 cm. It's a rare treat when a company changes the rear-centre length across the size range, but we need to do a lot more than that.
As you've probably experienced, tall riders are best served by companies making the longest of the long bikes, which suggests a "normal" XL or XXL isn't even close. A Trek Slash in size XL fits like a Nicolai G1 in size Small, for example. Riders at the ends of the height spectrum can't just use the bikes at opposite ends of a given company's size range; these outlier riders need to pursue entirely separate companies.
Sizing may still be a mess, but, as you noted, a few properly large off-the-shelf bikes exist for the first time in the history of mountain bikes. I think there's still room for bikes with the length of Nicolai or Pole, but without the slack head-tube angles those companies favour ... and their prices.