Did you pay for Priority Processing? If so, it should be much less than 12 weeks. Some people here on the forum who submitted using priority during January already have their visas.
If yours is non-Priority though, it could take a couple of months.
In terms of preparing, I think at the moment, it’ll just be a case of tying things up in the US so you’re ready to leave. If you have any pets that you are moving, or anything you need to ship to the U.K., you can start sorting those things out.
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