The Maemo bits that are open will continue being available somewhere, the only question is how long Nokia will be willing to host the closed bits.

The Symbian Foundation ran out of money and is winding down hosting, that's one thing. I expect Nokia will re-host those bits somewhere under nokia.com eventually, but to be honest who cares? Symbian was a classic case of "what if you opened the source and nobody came", a real community never formed around it and even the other founding members ended up abandoning ship. For better or worse there just isn't enough mindshare or interest out there for anything that's not POSIX or WIN32.