And Keselowski has no plans to return.
Keselowski on Tuesday signed a multi-year deal to drive a fulltime Sprint Cup and Nationwide Series schedule for Penske Racing beginning in 2010.
The 25-year-old native of Rochester Hills, Mich., will replace David Stremme in the No. 12 Cup car.
"My intent is to come to Penske Racing and build a home through the long-term future of my career," Keselowski said.
Keselowski had hoped to stay linked to Hendrick Motorsports after winning his first Cup race earlier this season at Talladega in a HMS-prepared car. He is third in the Nationwide Series standings in the No. 88 car of JR Motorsports, co-owned by Rick Hendrick and Earnhardt.
Hendrick said two weeks ago at Bristol Motor Speedway when sources revealed the Penske deal was agreed upon that he hadn't given up on Keselowski returning at some point.
"Whoever you go drive for just tell them don't get pissed off when I come after you," he said.
Hendrick likely will have to wait at least three years before making a run at Keselowski.
"We expect Brad to be with us for a long time as he has a great future in front of him with Penske Racing," said Bud Denker, the executive vice president of Penske Automotive Group.
Tim Cindric, the president of Penske Racing, agreed.
"I can tell you Brad, he's given us every indication he's committed to this decision and committed to making it work here," he said. "I'm not aware of any promises to go back or to have him back.
"Obviously, Rick and Dale Jr. respect what he's done. We're fortunate to have him here today."
Keselowski said Earnhardt made the decision, which he called the toughest of his career, pushed him to take the Penske deal.
"As surprised as that may be to some people, he brought up one of the good points that stuck with me when I made this decision," he said. "That was when you have the opportunity to grow and take on new challenges and you're capable of conquering those challenges you need to take it.
"You need to grow when you have the opportunity to grow in your career and as a person. This is a great opportunity for me to grow."
Keselowski said it became obvious fairly early in the process that he would have to look outside of HMS for a fulltime Cup ride. Hendrick closed one door when he announced that Mark Martin would drive the No. 5 fulltime again in 2010.
Another was closed when Stewart-Haas Racing showed no interest in putting Keselowski in a third car.
"Mr. Hendrick said he would keep working on different scenarios," Keselowski said. "And he did. He worked as hard as he could. He told me ... he worked much harder on my deal than he worked on Jimmie Johnson's or any [other drivers] to keep me in his camp.
"It became obvious it was just not in the cards."
Keselowski talked to many other organizations, including Richard Childress Racing. Penske Racing, which tried to sign him last season, was the best fit.
"Mr. Penske was extremely patient," Keselowski said. "He just sat there patiently and told me to let him know if and when whichever path I went down."
Said Penske in a statement, "We are very excited to welcome Brad to the Penske Racing family. Brad has shown terrific success on track the past several years and has quickly established himself as one of the top young stars in racing.
"He comes from an impressive family background in motorsports. He is a proven winner and a welcome addition to our team."
Cindric said Stremme has been told he is free to pursue opportunities outside of Penske Racing and that no decision has been made on his future. He added that Penske plans to run two fulltime Nationwide teams with Justin Allgaier in the second car.
As for Keselowski's crew chief, no decision has been made on whether Roy McCauley will stay with the No. 12.
Keselowski said it was a great relief to get the deal behind him. He added there are no plans to move out of his townhouse, on property owned and occupied by Earnhardt.
"He's been pretty cool about it," Keselowski said. "He's been one of my biggest supporters about this decision. If anything, we might grow to be better friends yet because we don't have to worry about the business relationship."
David Newton covers NASCAR for ESPN.com. He can be reached at firstname.lastname@example.org.