Pete,
Firstly let me say that i do see the Rights Managed model surviving, however it will never be of the volume and price point of lesser imagery, in fact you make a good point with regards to MP3's and downloads, but there are of course still people like myself who still buy CD's and in fact vinyl because it is of the quality required and mp3 is not. Now i know i'm in the minority as one who spends a fortune on a top CD player and turntable but i can tell you now that vinyl is very much having a revival right now, quality never dies.
I am presently having to re-evaluate my stock shooting, but am confident that there will always be a need for unique and inspiring imagery, and that clients will pay for this. It is as you say, going to be a difficult period of transition and clients are most definately expecting more for less, but dig in and don't let your standards drop.
Regards,
Gary.