This blog outlines the steps to take when renaming the Collaboration for Revit model. Renaming the model will not affect any users working on the model but for added precaution I would send out an email via A360 for everyone to sync the work then they can resume work.
In Revit open the model.
From the Collaboration tab click on Manage A360 Models
In the Manage A360 Models click on the Project you want to modify.
Select Rename from the drop down menu.
In the Rename dialog box enter the new model name and click the Rename button.
Once it is successful close out of the Manage A360 Models dialog box.
Sync the model and you will see the new model name in the sync dialog box.
This will be updated in the A360 folder but it will not update on the A360 website. To do this you have to publish the views.
HOW TO PUBLISH THE A360 VIEWS
From the Collaborate dialog box click on Views for A360
In the Views for A360 dialog box click on the select all dialog box then click on Save & Close. To find out more about publishing views click on the link at the bottom of the dialog box "How to select views for publishing to A360"
Your users will get a notification that the file has been updated and the new name will show in the A360 website.