The reality is that there is no release date because, as to date, there is no movie. Simple enough.
I believe Colfer has a script, or is working on it. Once the script is written it needs to get taken on by producers and directors, neither of which has happened. Then they start casting actors. Also not happened. After that they'll go into pre-production, shooting, and editing. Not happened.
There's no movie, and it's likely that there won't be one for a good year or two at the very least.