Simple question: Elements 10 is available for a perfectly reasonable price in the Mac App store. My principle reason for getting it would be occasional access to the somewhat improved ACR. Does Elements 10 support the latest version of ACR?
Plus you should check this page every once in a while for updates: http://www.adobe.com/support/downloads/new.jsp It appears that Elements 10, ACR 6.7 updates are available for both Macintosh and Windows, the same as for Photoshop CS5 (I think).