Occasionally we have questions that relate to issues in the Salesforce Platform - for example, JSON serialize is not handling aggregate results properly in Spring 13. When these are subsequently fixed, the question becomes moot.
So - what should we do? I think the answer is to close the question, since any further discussion/answer is unproductive. I wouldn't go so far as to delete, though, since it seems useful to have a record of regressions, in case a similar issue pops up again.
I think then, the consensus is to leave them as-is with a prominent 'Fixed in Season 'YY' message, resorting to protection if necessary. Thanks, folks!