Wallace was questionable in last week's game against Maryland and Washington has missed the last two weeks due to an injury.
Both Carter and Warren are considered first-round prospects in the upcoming NFL Draft.
Olesh was committed to Michigan since July 8.
The Nittany Lions faced two top 25 passing offenses earlier this season and allowed a combined 301 yards.
The Nittany Lions will face No. 1 Oregon in the Big Ten Championship game on Saturday.
Kortovich's commitment came just after Purdue fired its head coach.