In mergers and acquisitions, timing is the key.That truism is worth noting amid the swirl of speculation about Vivendi Universal’s entertainment assets. The film studio will have six films coming out between Memorial Day and Aug. 1 — double the amount of any major studio during that period. The list includes “The Hulk,” “Seabiscuit” and “2 Fast 2 Furious.” It is unclear how many will turn into hits, but the high-volume strategy could help Universal contend for the summer market-share crown. That could potentially enhance the perceived value of the Viv-U assets. The stock is another matter — stellar box office has done little to boost shares of AOL Time Warner or Sony in recent years. Vivendi topper Jean-Rene Fourtou has already made a few maneuvers to avoid the appearance of a fire sale. Suitors of the debt-laden company should expect him to draw their attention to the summer B.O. as bids are considered.