The last two national champions (Louisville and Kentucky) lost in the national semifinals the previous year. If the streak were to continue, then either Syracuse or Wichita State will win the tournament. Considering that both are the only remaining unbeaten teams this year, it would not be a shock for one of them to win.
Here are the past 5 national champions and their previous year's result:
2013: Louisville - lost to Kentucky 69-61 in 2012 in national semifinals
2012: Kentucky - lost to Connecticut 56-55 in 2011 in national semifinals
2011: Connecticut - did not make the tournament in 2010 (but did lose in national semifinals in 2009)
2010: Duke - lost to Villanova 77-54 in 2009 in Sweet Sixteen
2009: North Carolina - lost to Kansas 84-66 in 2008 in national semifinals
Here are the past 5 national champions and their previous year's result:
2013: Louisville - lost to Kentucky 69-61 in 2012 in national semifinals
2012: Kentucky - lost to Connecticut 56-55 in 2011 in national semifinals
2011: Connecticut - did not make the tournament in 2010 (but did lose in national semifinals in 2009)
2010: Duke - lost to Villanova 77-54 in 2009 in Sweet Sixteen
2009: North Carolina - lost to Kansas 84-66 in 2008 in national semifinals