I got lucky (kind of). The dealer had a sealed box with a brand new Mark IV in it. So I got mine in one day, last Friday. The downside was that I discovered that it is not a 2007 and may be as old as 2005. I have to get the serial number and find out from Mesa.
On the up-side, the amp is exactly the same regardless of 2005 or 2007 and the warranty is the same too.
I know it really sucks to wait once you finally commit to the purchase. I was told anywhere from 3 to 5 months depending on the run dates.
It is well worth waiting for though!