A few weeks ago Avid sent out an email to customers that basically said that at the end of the month older versions of Avid MC would no longer be available unless you already own a perpetual license for them. Adobe just sent out a similar email (except that it's effective immediately).
Is a patent troll afoot? Is this is an odd accounting regulation coming into play again? Maybe an odd bit of code (a codec? a plugin?) that is no longer licensable?