Excellent point, and I've certainly thought about this as well. I have the Incredible as well (not rooted), and I'm pretty certain that I'll be buying the Maxx pre-ICS. The Froyo and Gingerbread updates that I received went flawlessly so I don't have any bad experiences to keep me from just buying the Maxx ASAP and just getting the ICS update when it's rolled out.
Besides, coming from HTC and Sense, it'll give me plenty of time to really familiarize myself with the Maxx and all that Motorola has to offer. Then by the time ICS is served up, it'll hopefully go as smoothly as my previous updates have gone. In a nutshell, I don't want to be overwhelmed with having a new manufacturer, a new UI, and and new OS all at the same time!