I wouldn't mind having a migration path1 for RaspberryPi.SE. But I'm not sure that we can get one2 , because RaspberryPi.SE is still in beta. The statistics shows that we have migrated eight (8) threads over there in the last 90 days.
In the mean time, please don't hesitate to flag threads if you think that they should be migrated.
1 Similar to what we have for SuperUser.
2 Addition of a migration paths is done by SE mods (higher level than us stack mods).
3 Here's a year-old thread about expanding migration options.
This guideline of not migrating to betas is just one of the handful of migration guidelines. It came about, because migrated questions go live up at the destination stack immediately (there is no quarantine buffer), so a beta can potentially get swamped with migrations.
- A beta can not be one of the Off Topic → Belongs on a different stack options. So, migration to a beta can't be done by popular vote. Like us an SuperUser at the moment of writing.
- Migrations to neonatal beta stacks are strongly discouraged. The rationale is that a neonatal stack needs time to figure out what it's about without interference from the outside. I somewhat agree with this, but not completely agree. A lot depends on the details of the neonatal stack. As much as the neonatal stack needs to be left alone, it needs questions and traffic too.
After 90 days, a beta stack is no longer neonatal by any measure.
It makes less sense in case of mature betas, nor it's strictly enforced. It's a more of a guideline. A mod can migrate anything to anywhere (at the risk of the aforementioned mod getting flak, of course). The destination stack may reject the migration and advise the mod.
At the moment of writing, 70% of migrations out of EE.SE go to beta stacks. Only 7% bounce back.