It's hard to see anything other than a Forest win here, regardless of who plays. Forest will likely ring the changes but they have some quality depth in their squad, and a team that's won five on the bounce in the Premier League, while conceding just once, should have far too much for a Luton side that's struggling massively in the Championship.
Luton have been especially poor away from home, where they've now lost ten in a row, so Forest should win this one without getting out of third gear. Nottingham Forest 2-0 Luton.