I work in an environment where most enterprises still cling to IE6. These enterprises do so, because they've built up an internal expertise in keeping IE6 secure (kinda) and stable (kinda). At some point in the future, it seems like that internal expertise will be too expensive or will fail to maintain that secure and stable (kinda) environment. At that point, it seems, there will be a fairly quick migration to newer technologies. I don't think it'll be the killer app that draws the enterprise market... it'll be the bottom line.