Perhaps ... or maybe it's just that Canon's realised that people saw the 5D as overpriced for what it is, and are trying to move the bodies. At $5,000 Australian, it was more than I was willing to spend, so I bought a 20D instead. Now it's $3500 (after a $500 Canon rebate), and if I were buying a DSLR now, the 5D is the one I'd get.
I don't think it's due for replacement just yet - it was announced a little over a year ago. Give it another 6-12 months, I'd say. The 1Ds, on the other hand ...