I stated reading deadpool a little before the agent-x story arc. By that time we din´t really know why the took deadpool out and the gossip was that the creators of him had a disarrangement with marvel, and the later took the decision of replace him, witch of course didn´t work

is it true?

Liefeld is his creator, but not his owner. Marvel is his owner. They can do whatever the hell they want with him. So creator/owner disputes mean nothing usually. So this wasnt the case. Even now Liefeld must be cringing at the mere thought of them killing him off, since as he's working over at DC he has no right to know what they have in store for him any more than we do.