While this is complete rumour, The Inq has came up with a few conspiracy theories that doesn't sound bad at all, in any case come to think about it and the Athlon64 is very similar to the Opteron already, just running on different platforms optimized for different purposes, performance vs. reliability...

AMD IS BETTING its shirt on the x86-64 AMD64 architecture. The Opteron has been released and has delivered some impressive results. But there are already rumours that the Athlon 64 might be pushed back to next year. And there is evidence for an even more startling conclusion. There is evidence that could mean the Athlon 64 isn't just going to be pushed into next year, there is evidence that it could be pushed altogether.

As a side note, AMD keeps pushing their Athlon line, a new XP 3200+ chip is expected for the first half of May sporting a faster 400MHz FSB.