Big quote from the Adobe announcement.
"Flash Player 10.1 was also released to mobile platform partners to be supported on devices based on Android, BlackBerry, webOS, future versions of Windows® Phone, LiMo, MeeGo and Symbian OS,"

So we finally know that it has been released to Nokia and the holdup lies there and not at Adobe.
I think qole was right when he said that he knew for definate that Maemo will not get 10.1.
The only way the N900 will get 10.1 is through a community released Meego OS if at all.