If you _deactivate_ account you can keep using Messenger, and you are able to reactivate account in the future. Facebook doesn't delete your data. If you _delete_ account then Facebook will delete all your data and Messenger will be gone too.
Thanks! I didn't know this was possible. I was locked in Facebook because of the Messenger: that's how I communicate with most of my friends. I just deactivated my Facebook account and kept the Messenger.
Afaik when you deactivate your Facebook account, you have the option to keep the Messenger account, but just deactivate/delete the Facebook account.