Updated: Play.tm reported, supposedly based on information from UK retail sources, that the next Fallout: New Vegas add-on would be released on March 22. However, Game Informer has a response from Bethesda:

“ The info in that story is not correct. We will be letting people know the plan for upcoming Fallout: New Vegas DLCs in the next couple of weeks. ”

According to the now-debunked story, Honest Hearts was reportedly due to arrive in the UK, France and Germany on the 22nd of March on Xbox Live PSN and Steam. There have been a lot of hints at what can be found in the add-on in New Vegas itself and in Dead Money - check out this article for details.