Per the article below, it appears that Sling just submitted the updated app to Apple last night. As such, it will likely be several more days- and that assumes Apple does not kick it back for revisions.
http://bh.heraldinteractive.com/jobfind/news/technology/view/20100210slingbox_owners_will_soon_be_able_to_watch_tv_programs_on_iphones/srvc=home&position=also
http://bh.heraldinteractive.com/jobfind/news/technology/view/20100210slingbox_owners_will_soon_be_able_to_watch_tv_programs_on_iphones/srvc=home&position=also