...I'm not sure how many they will draw at Ford Field, but I'm sure the organizers are hoping that Michigan makes it to the Frozen Four. If so, I'll be there...
I was just looking through the records books. Although the round of 16 games are played regionally, the largest tournament attendance records were concludes in these cities:
139,170 (1989) - St. Paul MN - Harvard vs. Minnesota
121,261 (2003) - Buffalo NY - Minnesota vs. New Hampshire
117,970 (2006) - Milwaukee WI - Wisconsin vs. Boston College
116,848 (1990) - Detroit MI - Wisconsin vs. Colgate
116,147 (2007) - St. Louis MO - Michigan State vs. Boston College
Championship Game Attendance
19,432 (2007) - St. Louis MO - Michigan State vs. Boston College
19,324 (2002) - St. Paul MN - Minnesota vs. Maine
18,759 (2003) - Buffalo NY - Minnesota vs. Maine
18,632 (2008) - Denver CO - Boston College vs. Notre Dame
18,597 (2004) - Boston MA - Denver vs. Maine
Anyway, look for the attendance records to fall should Michigan win their next game. I'm not sure how many Ford Field will hold for their hockey setup, but 30K+ seems possible.