I believe the next hack-a-ton is in Berlin, soon.
Perhaps requiring people to travel to another country to participate in this is part of the problem. I don't doubt that real-life meetings are useful for Wikimedia Foundation employees and existing MW contributors, but it doesn't do much to encourage new people to join in.
We also plan to have two US-based hack-a-ton's a year, and I believe there is some form of one at Wikimania too. You don't always necessarily need to travel to another country to get to one.
I don't disagree with your sentiment though. We should likely make these events easier to attend online. We already put in the effort to mark bugs before hand, and we all work on IRC while at the event, so I don't see anything stopping online participation from happening. The hack-a-tons usually don't have presentations, so that part isn't much of an issue. We can likely stream out anything that needs to be, if it comes up.
I believe that in-person events are key for people to get to know one another, though. Maybe not everyone feels that way, but I definitely do. I've worked on MediaWiki for years, and I feel I know other community members much better since I've been meeting them in person, much more so than the years prior. The hack-a-tons may not be effective at bringing in new people, but I feel they are very effective at solidifying the current community that we have.
- Ryan Lane