You're right, ICANN should archive the namespace as it-is without removing the TLD from the root server and registry. Similar to an wayback archive version for domain names.

On the other hand .su (soviet union) is still in use.

It is very unfortunate ICANN still hasn't address this issue yet. Although not yet, .io is in a similar situation with even larger domains active but the territory is changing hands from britain to mauritius.

World is connected by Internet, it needs to be preserved even after geo politics and borders change.