Blizzard has taken control of the Blizzard.tv domain after a dispute filed with the National Arbitration Forum back in early November (As reported initially by Fusible.com found here).
The precise motivation behind this move remains unclear. It seems likely that at the very least this move is being taken to protect Blizzard against anyone else using this domain. Moves like this are common among media giants with precious intellectual property and brands to guard.
However, it is possible that the domain will be used as a convenient portal for all Official Blizzard streaming which includes things like BlizzCon and WCS. We will be sure to update you if any new information becomes available.