Warning: 4.9 will replace 4.8

I wish I'd known this before installing. I thought I'd be able to have both installed and try 4.9 and go back to 4.8 if need be. But on my mac the 4.9 seems to have replaced 4.8 and even replaced the icon in my dock.  It does keep my "recent" projects, but doesnt' seem to render as fast in Iray.