NuGet doesn't do automatic updating on it's own.
If you wanted to do automatic updating with NuGet, which I wouldn't recommend it against public packages (EF, MVC, etc), you’ve probably found it’s not easy to do. We've been using batch files to pull dlls off the network at build time for Continuous Integration, but this can get a little messy. We though NuGet might help us with dependency management between our teams/products, but we want to keep the continuous integration.
I did a quick search and found a few options.
Use myGet and at least you'd get notifications when there is an update.
http://blog.myget.org/post/2014/09/23/Notifications-let-you-know-when-a-package-is-updated.aspx
Then the team could do the updates. This is a manual update though, would require another check in, and wouldn’t work with nightly builds.
Change your NuGet.Targets file. I haven't tried it, but it seems like it should work.
http://netitude.bc3tech.net/2014/11/28/auto-update-your-nuget-packages-at-build-time/