According to this GI piece, Vivendi UK – and specifically the team looking after Sierra titles – is expected to take the brunt of any lay-offs as a result of the formation of Activision Blizzard.
From the piece:
According to senior sources the majority of the Vivendi team, which oversees the Sierra games label among other things, will face job losses – although some will be invited to apply for new roles in the merged company. Meanwhile the staff base at Activision UK will remain largely intact, it is understood.
Activision Blizzard senior management had previously intimated that a mixture of staff from both offices would be retained moving forwards.
More through the link.