Are there any plans to migrate these topics or individual questions to Expats.SE?
Presumably we'd need to get the Travel.SE mods involved, as they'd be the ones to do it. If they believe them to be on topic on Travel.SE, then there's no reason to migrate them.
Out of the 12 questions you link to, 10 are definitely on-topic on Travel. They aren't going to be migrated here just because they also may be on-topic here (and even that part isn't clear for all of them).
Only questions that are off-topic where they are (or at least borderline, and clearly on-topic elsewhere) may be migrated elsewhere.
To the best of my knowledge this wasn't done elsewhere in StackExchange. Stackoverflow still have old UNIX, Magento, Ubuntu questions even though they may not be related to programming within those environments.
So I don't see a reason to migrate the questions out of travel.SE that existed prior to the existence of this site.
There's no reason to send them over here - there's not much for folks here to do with them other than notice that they exist. We strongly discourage 'bucketing' of content simply for the sake of it, or for content generation.
We have no problems when it comes to generating our own great questions, so we don't really need them. Additionally, it usually ends up with just a bunch of gray 'anonymous' faces attached to the posts.
If you think a great question was asked there that would be nice to have here, then put your own spin on it and just ask it here, let this community answer it and make it your own.
Additionally, mods on any site can't migrate questions over 3 months old. The migration system is in place to give the question author a better experience. Please don't migrate things when it's doubtful that the person that wrote the question has any interest in it any longer.
For new stuff, yes, the mods on both sites can work that out. If it's a week or less old, then we might just get a new contributor along with a great question, so it's a clear win. Otherwise, it's more of an archival thing, and not really all that helpful.