Mergers don't happen because of what games could become...it's a "money thing". I bought shares with Activision-Blizzard and they keep going up (even if the industry seems to be going down lately). So this merger is good for many things; here's a link that might help you better understand the real game.
http://uk.reuters.com/article/governmentFilingsNews/idUKN1127768620080711
How will it affect the costumers (gamers)? Well, that's not as much of a concern (for the financial market). If you have good statements with a strategic plan that can deliver good financial reports, then stockholders become confident in your doings and it boosts your shares over time.
These "merger" decisions aren't taken by the producers, they are taken by the board of directors/shareholders/CEO/ETC.
I'm both in the financial market and a gamer. Financially, it makes sense. As a gamer, I have the same questions as you do. Here's another example of what makes sales go Woo hoo...
http://www.bloggingstocks.com/2008/...es-during-q1-thanks-in-part-to-kung-fu-panda/. Kung Fu Panda is far from being the biggest blockbuster game...but look at the sales and how it boosts the company's statements. That is what drives companies to make such games. It's a little more complicated than that because you also have to target different niches in your market but still.
Otherwise, could you imagine what kind of game would come out if Valve, Blizzard, Activision, 2k Games, and Codemaster formed a partership to create one game! Wow, crazy eh. I'd love to see that!