What if we got our hands on a 70mm blow up wouldn’t that have preserved far more detail ? Thus warranting a 6.5k or 8k scan.
A 70mm blow up print does typically have slightly more detail than a 35mm print, even though they’re both based on a 35mm negative, due to the quirks of optical duplication. But it would still not have enough fine detail to justify anything above a 4K scan, because optical duplication, even for blow-ups, loses a shocking amount of fine detail with every step. The three Star Wars 70mm blow ups I’ve seen confirm this.
The root problem remains the same: a pristine, 35mm negative of modern high-quality filmstock could be worth a 6k scan, but we don’t have anything near that. We already have access to extremely high-quality prints, we already have access to 70mm blow-ups. They just aren’t worth it, because even the best prints aren’t anywhere near the quality of a negative. Re-scanning prints with a better scanner, or with a multi-pass HDR scan at 4K would yield far more usable results than a >4K scan.