I had a doubt that this merger (if succeed) will have any impact on Google. Microsoft doesn't have a good record in past
They have acquired hotmail for $400 million but failed to make it the market leader in email space. Even today Hotmail users are still confused with live ID or Passport.
In comparison Google have more user friendly options and it saves time as well as have the most powerful search technology. To me Google will soon eat up the competition until and unless some one come up with a better search technology. That's the dominance, No #2nd or #3rd SE.