The Next Big Thing is going to be/currently is (with respect to Computers, The Internet, etc): Virtualization. Specifically by replacing apps-on-your-harddrive with apps-online. The practice of virtualizing applications, OSes, hardware, and sometimes even whole computer systems has already been ongoing for some time, but now we are seeing, and are going to see a lot more instances of individualized virtual desktop environments for end users that exist solely or primarily online.
As I write this (at work) I'm connected to livejournal's built-in journaling web form from a Citrix Remote Desktop.
Things like this:
Desktop On Demand will become more and more common.