There's no need to speculate -- we already know:

1) If the NCAA seeded every team 1-68 (and this includes the Auto Bids), and then 61-68 played the play-in games......every play-in game would involve a low-major Champion.
2) "then it is indirectly saying teams seeded below the "Last 4 In" probably wouldn't be selected to the Tournament if no conference received an automatic bid (assuming the Committee selected the best 68 teams for the Tournament)" -- we can get rid of the probably. If the Committee thought a team was good enough to make the Tourney at-large, they wouldn't seed that team @ 15/16.

How do we know this? Because no at-large has been lower than 14-seed (BYU, Iona).