According to Brian, we already have Cortado up and running, and it can support video playback for about 80% of people who use Safari or IE on desktop machines. That is significant, even if it’s not the ideal long-term solution.
Just for reference, the 80% number comes from http://www.w3resource.com/browsers/java-support.php , which claims 84.4% of their users have java enabled. This should be considered only a rough estimate as that's site's visitors may be a different demographic than ours, and java installation is probably not evenly distributed across platforms. Nonetheless, probably a significant amount of users in the IE/safari category have java enabled.
Based on http://stats.wikimedia.org/wikimedia/squids/SquidReportClients.htm , 84% of desktop sfari/IE is about 12% of our user base in total.
--bawolff