I've heard this from a few sources already so I am posting this up. Apparently Antix has released a press release stating that the next Most Haunted Live will be shown in October. Here is what was released.
Posted 4th June 2009: Upcoming events: Due to much speculation around various forums we have decided to allow information to be released, We can confirm that the next live event will be held in October for the Halloween special. We are still debating whether to do another full 7 nighter as last year so keep your eyes peeled as to what comes along
--ripped from digitalspy forums--
So the summer solstice live from Venice, Italy has been canceled so they can get ready for the Halloween Live.
If we find out anything else we will post it for you all to see.