Ok, two people dropping may be a problem. I'm not ending the group, but I may start over with new plots if everyone is ok with that. That gives us some options. You can keep your characters, make new characters at your level, or start over at 1st. If you keep your characters the history and backgrounds will change because it will be a different world.
Either way I have and idea for a campaign, that involves a really fantastic setting that I've wanted to use for a while. Let me know what you want to do as far as your characters, and I'll work up a background. This will not be in the Nentir Vale, so I'll probably be starting over another board, or renaming this one (if I can).