There's no option for users to migrate from meta to main, because that only ever happens once in a blue moon - there's theoretically no solid grounds to enable that migration path.
The current way to migrate from meta to main, is to custom-flag for moderator attention.
Looking at migration stats for meta (are those accessible with 10K privs?), looking at meta-to-main migrations:
- 1 question was migrated in the last 90 days
- 2 so far in 2016
- 12 in 2015 (9 in the first quarter)
- 4 in 2014
- 6 in 2013
- 6 in 2012
- 7 in 2011
I think Q1-2015 was just weird, IMO 1-2 migrations per quarter wouldn't be enough to warrant a migration path.
On the other hand, I'm all for community-driven moderation, so I'm totally for it anyway - there's a migration path from main to meta already, and that migration path is even more seldom:
- 1 in 2016
- 2 in 2015
- 0 in 2014
- 2 in 2013
- 2 in 2012
- 2 in 2011
In light of these stats, I say go for it.