The biggest obstacle for the Cajuns at this point is the quantity of #1 seeds that can potentially host in the immediate geographic region. Also consider that the West will likely have four regionals this year instead of three (taking away a potential host site elseware). The West has had four regionals only twice (2003 and 2005). But the play out West this year is solid and the national champion came from the West last season when it was only awarded three regionals. Also, the West has more representation on the NCAA Selection Committee this season with the addition of Arizona State coach Pat Murphy (which could also be a positive for the Cajuns' chances provided they play well in Tempe).
I do not think the Cajuns will need to be a Top 8 RPI team, but they will need to be a stronger #1 seed than one or more of the #1 seed hosting candidates in the nearby region. Currently, Rice, Texas, and Texas A&M are obvious candidates to host. At this point of the season, all three have stronger resumes, have better facilities, and stronger attendance than that of the Cajuns. You can say the same for Arkansas, Mississippi State, and Mississippi. But the NCAA is not going to award seven regionals in the Louisiana/Mississippi/Arkansas/Texas region. They have awarded six regionals to this region only twice (1999 and 2003). If you add the state of Oklahoma to this region, they have awarded six regionals to this region four times (1999, 2000, 2003, 2004). Never has the NCAA awarded seven regionals to the Louisiana/Mississippi/Arkansas/Texas/Oklahoma region and more than once they have awarded only three. The Oklahoma Sooners are also a candidate to host which crowds the regional field even more. However, if the Cajuns are the only viable Louisiana hosting candidate, this will help.
Another thing to consider is that typically two or more #1 seeds do not host a regional. It has never been the case that all sixteen #1 seeds have hosted regionals and only three times have 15/16 #1 seeds hosted. As many as five #1 seeds have not hosted a regional in a given year and three times (1999, 2000, and 2001) four or more #1 seeds have not hosted regionals. Although, the recent trend has been that 15/16 #1 seeds have hosted regionals (three of the last four seasons). Hence, you can virtually count on at least one #2 seed hosting, typically in an effort to balance the regionals geographically. This is not in the Cajuns' favor.
In summary, keep an eye on what the leading hosting candidates in the Mississippi/Louisiana/Arkansas/Texas/Oklahoma corridor do the remainder of the season. If they can pass a couple of those schools, they will have a shot. But the competition is stiff.
Brian