The only way I know would be with a widget using the YouTube API in AS3. That way you can listen for the end of the video and continue to the next slide when it is complete. You would not use the YouTube Interaction. If you are publishing to HTML5 you may be able to use JavaScript to listen for the video end as there is also a JavaScript API for YouTube.
I have built quite a few ads for Charter Cable using the AS3 and JavaScript API's.