The NL is beating the AL in home runs as of June 15, with Albert Pujols, Raul Ibanez, and Adrian Gonzalez all with 22 home runs. You still can't count out Carlos Pena and Mark Teixeira with 20—it'll be close till the end.
After the All-Star beak, Albert Pujols will fall apart trying to swing for the fences rather than playing the game to help his team. Doing this, he will fly out, ground out, and strike out.
He has to remember that hitting singles are better than loud fly outs. He also can be waiting for a perfect strike, but the pitchers aren't and never leave a hanging breaking ball down the heart of the plate.
He has to go get to stuff on the outer-half of the plate. He has to help his team and home runs will come.
Adrian Gonzalez will keep his game up with singles, doubles, and homers. If he does not try to swing for the fences and keeps his nice smooth swing, he will stay at the top of the home run chase.
Mark Teixeira is lucky he gets to play in the new Yankee Stadium. He has an advantage. But when he goes on the road, he has to swing harder which causes him to strike out or top the ball sending it into the ground. He will be in the running till the end.
There is always a long shot in this case. I would say it would be Mark Reynolds with 17 home runs playing for the D-Backs. He can hit well. Now with only a few years of experience, he has a lot of potential and will be a young stand out. He will not win it this year, but will finish with a lot of home runs.