NBC is canceling the third hour of  Today  to make way for new star Megyn Kelly, sources exclusively confirm to Page Six.We re told Kelly will take over either the 9 a.m. hour from Tamron Hall and Al Roker or will replace Hoda Kotb and Kathie Lee Gifford. If she takes over Hoda and Kathie Lee s 10 a.m. hour, they will move to the 9 a.m. hour,  an insider said.We hear Hall will be leaving the network next month when her contract is up. Roker will continue his 7-to-9 a.m. duties.Kelly will start in September. Everyone has been left in the dark and no one knows why there s such a disruption when shows are doing so well across the board,  an insider told us. Another insider adds:  People are pissed. The third hour was beating every syndicated show across the board. They were in over their head and bit off more than they can chew when they hired Megyn.   NYP 