How should I launch pricing plans for my app?

I've been working on #unmarkdocs for a while, and I'm about to finally launch a premium plan. How should I announce it to existing beta users? What should I do with existing users?

Is the premium plan a bunch of new features that weren't available in the beta? If so, I'd say just release them and send out an email.

If the premium plan is going to lock features that current users already have, I would put a delay on it going into effect for them... Send out an email saying they will be able to keep using the premium features for like a month or whatever, then they will lose them. Throw in a coupon code or another offer to help convince them to upgrade.