This excerpt taken from the ATVI DEFA14A filed Dec 11, 2007.
2. How will this transaction affect Activision unvested options? Will vesting accelerate as a result of this transaction?
The vesting of stock options is defined by the Stock Option Award Agreement. Agreements can vary from plan year to plan year.
We are currently reviewing all individual Stock Option Agreements to determine if any special vesting provisions will take effect as a result of the closing of the transaction.