My team is using ProjectServer 2007. Our enterprise is currently running the enterprise version of SharePoint 2007. So great, no problem. However, the enterprise is considering upgrading to SharePoint 2010. If this happens does it mean that we will also have to upgrade ProjectServer as well to keep the integration between the two?
Project Server is installed on top of SharePoint both in 2007 and 2010. You cannot upgrade the SharePoint server that has Project Server on it without upgrading the Project Server instance.
If however the Project Server is on a SharePoint server that is not in the "farm" then it is possible to upgrade SharePoint without upgrading Project Server but this means that Project Server is on a separate machine from your other SharePoint servers and that they are not joined to the same farm.
I agreed with David’s statements. Here at our company we upgraded to 2010 on both Project Server and SharePoint. On the project server upgrade, here are a few notes (lessons learned) which you may want to consider:
1) If you are going to upgrade project server to 2010 and having the "Project 2007 Compatability Mode" turn on, just remember once you do decide to turn it off make sure that a) all projects are saved/checked-in/published, b) PS server admin open and save the enterprise template and project server templates using Project Professional 2010.
If you failed to do so, you may have your projects files out of sync on the proper versions. It will be a mess to clean it up afterward.