I don't think the post-quantum block collision scenario is very plausible, and, at any rate, it's effectively an online attack (sweet32 follows the attack model Thai Duong and Juliano Rizzo came up with, where you're relying on malicious Javascript to trigger it). If we get to plausible quantum attacks of any sort, algorithms will get swapped out to regain security margin.

It's not like other quantum issues, where you're worried about transcripts collected today being broken 15 years from now.