Can I upgrade my .net 4.8 webforms webapp to .net 5.0?

I have a medium-sized Web Application project on Framework 4.8. It has Webforms and MVC (and webapi) in it. I am confused by the recent 5.0 announcements that seem to indicate that everything should now be 5.0. After downloading the new SDK, and Visual Studio 16.8 preview4, I am still not able to change the target framework of my main webapp project in its settings. Am I missing a step? Can I upgrade my .net 4.8 app to 5.0?