re: 2015 Beisbol: game over

16 teams host regionals. It is mainly based on merit, but some other factors like location and regional site (i e no shitty small ballparks) also factor in.

The top 8 are ranked 1 through 8. Like you said, they host the super regionals if they advance. 1 thru 8 are matched up with 9-16 (not ranked in any order) based somewhat by region. So #1 A&M could face the best not national seed TCU because it's a regional match up, but that isn't always the case. More than likely there will not be enough good teams in a single region, but like I mentioned earlier there is some consideration for location.

If a national seed does not advance it almost always goes to the other regional host assuming they advance. If neither then it kind of goes by if they made a bid, who's bid / host site is better, and who is higher ranked (the 2 seed would likely get it over a 4 seed).