The UFC had to cancel its UFC 145 card in Montreal citing the absence of a worthy main event. The company is planning a return to Montreal some time in 2012 but does not know the exact date. There is already speculation that the date could be some time in November when Georges St. Pierre comes back from knee surgery. GSP recently confirmed his rehab was going well and would like to return to action near the end of the year.
Update 3/21/2012: The UFC announced today that it will host three events in Canada in 2012. Calgary will be the host of a Jose Aldo fight on July 21 although an opponent has not be named, Toronto will host UFC 152 in September, and Montreal will host UFC 154 in November.
Update 4/24/2012: With UFC 147 losing the Silva Sonnen II title fight, Dana White confirmed they are working with Jose Aldo on filling the spot. The opponent most likely to take the fight against Aldo on short notice would be Erik Koch who comes out of the same Duke Roufus camp as Anthony Pettis. With UFC 149 losing out on Jose Aldo, White said its possible Jon Jones vs Dan Henderson could be the main event for UFC 149 in Calgary, Canada.
Update 5/7/2012: Jose Aldo vs Erik Koch has been confirmed for UFC 149 in Calgary. The card will also feature Shogun vs Thiago Silva, Big Nog vs Cheick Kongo, Akiyama vs Thiago Alves, and Michael Bisping vs Tim Boetsch. UFC 149 rounded out nicely considering the promotion had to scramble after potentially missing out on Jones vs Henderson and even Aldo vs Koch.
Update 6/9/2012: Add Jose Aldo to the list of injured fighters. Aldo suffered an undisclosed injury and had to pull out of his title defense against Erik Koch. There is no news on what will happen to Koch but the UFC said the fight has been postponed. There is currently no timeline for when Aldo will be able to return to action.