I looks like the UK Asus Facebook page let slip the dogs of war... Actually, there was no war, and no dogs either, but they did share that the OG Asus Transformer will probably get an Ice Cream Sandwich update sometime shortly after January 12th. Astute readers will notice that that date is the exact date that the Transformer Prime is supposed to get the Android 4.0 goodness. They indicated that they are working hard to get it out as quickly as possible after that. Here's the direct quote from their Facebook page:

ICS 4.0 will be coming to existing Eee Pad Transformer TF101. Exact date TBC but we are working on making the FOTA update available a.s.a.p. after Jan 12th launch with Prime TF201.
This is pretty fast to crank out ICS support considering, and good news for owners of the Eee Pad Transformer.

Source: TransformerForums via Droidmatters and Facebook - Asus UK