Hmmmpff....
@Jedit... Yeah it could well get pulled. Whilst I believe the iDevices are great devices, work well, etc. this article, and the 4S release just shows why I will NEVER consider an iDevice again (I have owned 2 original iPhones).
Siri WAS available as an app pre 4S (yes not as well integrated, etc), and now the people who used it (admittedly not that many probably), had it removed, and are forced to upgrade if they want to continue using an app they previously used... There is NO reason at all for Siri not to be available for any device iOS 5 is available for, but it could be released, and might be restricted now due to the load that must now have been thrown at the apple servers. At the end of the day I guess most people will play with this and then not use it, demand drops and they could roll it out, we'll see.
But if I was a current iPhone user, using Siri and it now being removed, I'd be really annoyed right now, and there have been plenty of other examples of apps being removed...
Who knows if they'll remove Vlingo or any other similar app in the future, and thats the problem, I don't know, and it can't be guaranteed.