I've just noticed that Magento stack is in Beta, whats the policy regarding new topics made on webmasters during beta phases of stacks?
Do we flag them as off-topic and recommend they go to Magento Stack or answer?
I would flag them for migration if they look like they are magento specific questions: i.e. they wouldn't be applicable to someone who wasn't using magento. If it looks like other webmasters could benefit and learn from the questions, even if they aren't using the magento software, then it should probably stay.
The guidance in the past has been to not migrate questions to beta sites, even if such questions are more appropriate on said sites. The logic being that a beta site should be able to stand on its own, instead of being supported initially by migrations from other sites. Reasonable enough.
If a target site makes it past the beta period to graduation, then migration may be possible. Keep in mind that if a question would be considered on-topic on, say, both Stack Overflow and the Magneto site, the question would be welcome on either site.