Just yesterday, ASUS promised both TF201 and TF700 owners their Jelly Bean updates on September 28th and 29th, respectively. While they owned up to that for the Prime, the Infinity isn't so lucky: they just had to push the update back.
According to ASUS rep Gary Key, "a couple of applications that were recently updated (Facebook 1.9.10 on 9/20 as one example) required a last minute firmware update for the keyboard to operate correctly in the "Comment" area with Android 4.1."
It's not all bad, though - the update should still begin rolling out early next week. Personally, I'd rather wait a few more days for a fully working OS than have to deal with a buggy system right now, anyway.