There is no mention of this in the document, but the timing suggests there may be a GPDR-related factor. It's hard to get consent from users that haven't touched the service for years.
That's an interesting point. I wonder if at some point in the future we'll start getting historical exemptions, similar to those for real world properties with historical value.
It might even free up faster innovation in technical law, since new laws could be as onerous (or not) as lawmakers wish.
I agree and think it is clever marketing. They may not have permission to email their users promoting their new service, but telling your users that "your data is being moved" is a requirement isn't it? Now that in theory it is in the hands of a new service.