Yes, you can have both. I'm running WF4, WF5, Creo 1 & Creo 2 on my PC. (I only have active projects on WF4 & Creo 2 at this point.)
You'll need updated licenses from PTC, of course, and you may need to install the license server from Creo 2. I think WF4 should then be able to use the Creo license server but I doubt Creo 2 will see the WF4 server. You could give it a shot, worst that would happen is that Creo 2 would fail to launch saying no licenses available.
Just pay attention at install that it's not trying to do an 'upgrade' install where it would wipe WF4 out in the process. I don't think it will by default, but pay attention to be sure.
You can use the same license software installed for WF4, just load the new license showing Creo2 availability. I have WF3, WF4, WF5, Creo1 and Creo2 all running from a network location against the same license file.