It would drive people to Office 365 which MS wants to be the future of Office and into subscriptions.
At a minimum I would like to think they will update the Mail app. If they put out a well featured robust mail app, the majority of the target audience of Surface RT should be well satisfied. People looking to use RT as a cheaper-than-Pro corporate device will yell and scream about the lack of Outlook if they think MS can do it and is choosing not to. But that is MS's prerogative if they prefer to drive corporate use to the more expensive Surface Pro (there are cheaper options from MS partners corps can always use instead).
I would love to have Outlook on my Surface RT. The mail and calendar apps need major improvements. Calendar really bugs me that I still can't set up a reoccurring appointment other than some basic case that are not useful. How did Microsoft lose these basic capabilities that they set as standard with Outlook?
My guess is that it is based on the Phone 8 Outlook Client (code base) with UI changes to function on the 16:9 screen on the Surface. If it is it would be awesome as it would allow Notifications and Combining of Inboxes and would kill the battery as it would still use the native or at least separate calendar app and maybe even POP3.
I'll be happy with a version of Outlook running on Windows Phone 8. It has a feature that allows me to do schedules, i.e., accept, decline, tentative, and it automatically goes into all my calendars (Live account).