Although the collaboration album of Kendrick Lamar and J. Cole was announced four years ago, there's no confirmed piece of information that can prove that the two have already started working on the project. With this, rumors claiming that the planned collaboration album has been shelved is growing louder and louder more than ever.

According to multiple sources, the cancellation of the collaboration album is caused by the hectic schedules of both Lamar and Cole. As the two are busy with their respective commitments, their time won't jibe, and the album can't possibly take shape.

Lamar is said to be currently tied with his promotional stints for Reebok's "Classic Leather" line, which is believed to promote unity, hence, making Lamar a perfect endorser.

"Kendrick represents an authentic voice within today's pop culture. Similarly, the Reebok brand represents innovation and authenticity in the marketplace. There is a seamless and organic relationship between Reebok and Kendrick Lamar which makes him the right fit for this collaboration," said Damion Presson, Reebok's director of entertainment marketing, in an interview with Billboard in June.

Apart from his Reebok commitment, Lamar is also busy with his series of concert tours that began last month. According to an earlier report, the rapper will be busy with his world tour concert until the month of September.

Nonetheless, it is not only Lamar who has a packed schedule as Cole is just as busy as he is. According to the listing of MTV, the rapper has five scheduled concerts beginning this Aug. 5 until the month of September.

However, fans are still hoping for the two to finally sit down and proceed with their collaboration once they are done with their current commitments. It's interesting to note that both Lamar and Cole have no reported schedules after the month of September.

Will they finally start working on their collaboration album by October? Have they already started working on the album and might probably resume when their schedules permit? 

Without any word from both parties, fans can only hope and wait.