Re: how close is OpenPGP tied to SHA1

If this WG finds a solution to this issue, e.g. by switching
everything to SHA3. What will happen to already existing keys?
I mean would it become necessary to create new keys in order to fully
benefit from the swtich?

Could there be problems with the already existing signatures using
(probably) SHA1 and downgrade attacks or similar things?

Greetings,
Peter