Can I predict the release date?
Yes. To do this, set the start date of the release, and enter the expected velocity per week in the release. This is done in the popup dialog for the release:
You can specify the best-case, expected, and worst-case velocity. If you only want to specify one velocity, it's most useful to specify the expected velocity, since that is used for most predictions.
The velocity should be the sum of the expected velocities of each team that works on the release. You can see the velocity of each team in the popup dialog for the team. You can also see the velocity across all teams by clicking the link "Show velocity in this project" in the popup dialog for the release.
Note that the velocity charts show the velocity per sprint, not per week. You must calculate the velocity per week yourself, based on the velocities shown in the charts. Also, note that the velocity charts don't include work done in Kanban boards. You must calculate the velocity of work done in Kanban boards yourself, if relevant.
When you start the release, you will be able to see the predicted release dates in the burnup chart for the release, as a green dotted line for the best-case, a gray dotted line for the expected case, and a red dotted line for the worst-case: