Who needs an "official" ICS? I've installed a beta ICS ROM (teamDRH) on my Viewsonic gTablet and it is as tabletized as honeycomb, though it looks better (this build has issues, but developer support is pretty impressive). The best Viewsonic could do as an update was a Froyo-based bugfix release.

Besides, people who have installed custom ROMs on their phone/tablet are likely less worried about using alpha/beta software, so I wouldn't be surprised if most of the early beta testers will be from this group.