They will work, for the time being. However, its always best practice, as with any other software, make the client and server run the same version. In case of trouble, the first thing Support is going to ask (reasonably) for is to update the plugin as well.
Note that, for example, if the rendering engine had any bug in the SR1 that has been fixed in the SR2, the issue will still happen as long as the version differs.
Hope that helps.