Meyer has two seasons of eligibility remaining.
Allen was most recently the head coach at Indiana, a position he was fired from in November.
"I'm coming back, and why does that need to be announced? That should be the expectation."
Wallace is the fourth Nittany Lion to declare for the 2024 NFL Draft.
Jacobs is the third Nittany Lion to declare for the draft.
"We made a pact as a leadership group. We're committed to this team."