Wow! Congrats! And thank you for sharing.
It is expected, yeah. The way that you handle their feedback now is crucial. Address their comments, make sure they feel heard, and highlight the improvements and new features (I’m sure there are many!). If you have any trouble with the feedback, post it here, and I’d be happy to help.
Take a look at the last section of this article, it’ll give you some pointers: How to prepare your community for a Discourse migration