As Frostfyre pointed out, the question isn't currently at risk of being deleted. The system won't automatically delete it, and at this point, manual deletion by a mod is probably the only thing that would get rid of it. The only thing that could happen to it is that it could get closed by the community, which honestly wouldn't be a terrible thing. Many old questions that are deemed out of scope at some future time are closed, and that's okay. Honestly, I don't think that would happen to this one, because I can't see a strong argument for doing so.
A historical lock can only be applied or removed manually, by a moderator. It just takes four clicks through a menu. If you think a post should be locked in this manner, you could raise a mod flag, but asking a question on meta might be better. I think that a historical lock to some extent implies that the community as a whole deems that the question is one of a select few that deserves this status, and that probably should lead to a quick meta discussion.
That said, I think a historical lock would be inappropriate, because this sort of case isn't what they're for. Historical locks are reserved for truly significant questions that clearly no longer meet the site's standards. In particular:
Questions can be historically locked when:
- The post does not meet the current guidelines for a good, on-topic question, and
- The post is stellar, in spite of its off-topic nature, and
- There are a large number of views, upvotes and inbound links on the post, and
- The post is contentious; e.g., it has been closed and reopened at least once, or deleted and undeleted at least once.
The question here has never been closed, and I honestly think it doesn't meet any of those four criteria, let alone all of them. The question has now been closed (partly via a mod hammer), and currently has three reopen votes, so it's arguable contentious to some degree, but it still fails to meet the other three requirements for historical locking. Therefore, I'll argue that the question shouldn't be locked (note that it has now been unlocked, after it was initially locked).