This is the second time I've heard this rumour, but no one seems prepared to back it up in any way.
Frankly, I don't care one way or the other, because if you like the amp you have and maintain it well, it will still be working by the time you're incabable of even picking up a guitar. These amps are bult like tanks. I've heard guys playing through original Mark Is, and they still sound stunning and induce goose-bumps in the right hands.
What's good is that whenever they discontinue a line, it never seems to be due to any inherent problems with them - it's almost always because they have somehow come up with something a little better, a little easier to use or just something with a slightly different twist. I can still remember when the first DCs came out, going down to try a DC-3 (at the time I was using my trusty studio .22) and I was blown away. They got it right - it was basically the same amp, but more user friendly, with everything the studio .22 needed but didn't have.
I'm sure that if the rumours are true, Mr. Smith has something very clever up his sleeve to take the place of the F series. As for me, I have everything I've ever wanted now. I have my DC-3 which still sounds incredible, and my F-50 is for me my dream amp. It sounds incredible, it's a dream to play, and it's very easy to use. I couldn't ask for more.
The one thing I would LOVE to see is a re-issue/replica IIC+. If they did it right, I'm sure they wouldn't be able to make them fast enough. But the one thing (with the exception of the Mark I reissue, which arguably is not an exact replica) that Mesa never does is go backwards. I bet that one day we'll see a Mark V that will incorporate a specifically voiced IIC+ lead channel.