Last night Chris Rankin updated his Twitter account with some very very exciting news.  He said:

in the hotel, excited for filming in the morrow, but not excited for the 5am wake-up call… 43 principal cast on set tomorrow…!

This is only an assumption but I, and many others, are guessing this means that the Battle of Hogwarts scene is being filmed!  We also know via Twitter that Matthew Lewis, James and Oliver Phelps, and Warwick Davis are also on set this week!  Matt had also mentioned the following on his twitter on Tuesday:

Well that was an awfully short day at work. Rest of the week won’t be as easy if this morning’s rehearsal was anything to go by. Love it.