On the 6th of April, 2013, Steve Jaros, the "Writing Lead" for Saints Row: The Third, confirmed via twitter than "Saving shaundi" is the canonical ending of Saints Row: The Third.
Link to his twitter post: https://twitter.com/SteveJaros/status/320517632040243200
Therefore, at the end of Saints Row: The Third, the Magarac Island statue is still standing, the Daedalus attack never happened, Steelport is not a city-state, Shaundi, Viola, Burt Reynolds, Cyrus Temple and Killbane are alive, while Kia is likely dead. I say "likely" because canon deaths are usually shown in cutscenes. You must "kill" Maero to complete The Siege, but he still comes back for the next mission.
Anyone who thought that Killing Killbane was the true ending is wrong, and anyone who edits the wiki to change the facts will be blocked from editing. This link has already been used as a reference in several places, and should continue to be used as reference where-ever necessary.