We are committed to improving the project and keeping it open. As a member of the Cyrus IMAP board, I'm very proud of the 3.0 release that we recently made, and we're currently planning for the 3.1 release which will include further significant improvements.
I often worry about infrastructure projects like IMAP, SMTP, DNS, SSH, OpenSSL, etc. They often have very small teams, mostly volunteers, and the implications of a bug, particularly a security bug, can be catastrophic. And, if something we rely on were to be abandoned, we'd probably be screwed; even in cases where we have the technical ability in-house to maintain another major project, we don't have the time (or the budget to add more people to our small team).
Though admittedly I'm inclined to move the customer I have using it to Office365 hosted Exchange since they recently decided (against advice) that it was Very Important that their users start using Outlook which has meant a shift to local PST files.