As with most application upgrades, I go through a period of using both the new version (while I'm learning) and the old system (because I just want to use or enjoy what I am very familiar with). This was certainly true of every new version and upgrade in the Civilization series since Civ 2. I have a seemingly reasonable fear that Steam might force me to use only Civilization 6 once my purchase has been completed. This would be enough of a reason for me to postpone purchasing Civilization until I am absolutely ready to make the switch. I would prefer to pre-order Civilization 6 and leave it on the shelf until I am ready to begin learning. Can somebody with official involvement with Civilization help me understand whether Steam would allow me to play Civ 5 after Civ 6 becomes available?