TriJuice.com has this to say:

"Moving the [Arizona] race to November causes a race option dilemma for triathletes, which Ironman race to participate in; Ironman Florida or Ironman Arizona. No need to worry if those races sell out, which they do, there are two other iron distance races in the month of November. We now have the new kid on the block, non-WTC, iron distance race called Beach2Battleship which is also scheduled to take place in November in Wilmington, NC and then the Silverman triathlon race which is in its 3rd year in Henderson, NV.

http://www.trijuice.com/2007/11/ironman_arizona_moving_to_november_rumor_is_true.htm

Also, keeping in mind that Ironman/World Tri Corp is only a licensing agency, to get an April Ironman there would likely need to be a pre-existing April Iron-distance race that Ironman/WTC could sell their name to. And according to trifind.com, there are no April Iron-distance races in the US.

http://www.trifind.com/iron.html

IMKY is the only US IM race run by World Tri Corp. IMWI (like all other US IMs) is run by Ironman North America. (Unless this has recently changed). So my thought is it would be tough for them logistically to run two events in November, but they are real bright guys with lots of resources so I guess they'll manage.

There was talk of IM Vegas, I think for around that time from but that has since fallen through, not enough community support.

November might even be busier as we might see another WTC IM race with IM Mexico / Cozumel in 2009. Mexican TV and newspapers have been talking about it but nothing official from WTC. I know there was a group from Mexico working on getting a race there in 2009, so it's highly likely that this is true.

Although IMKY and IMCanada were the same day, and North American Sports (formerly Ironman North America) runs both of those... so IMWI and IMC were run a week apart just fine ;)