In terms of map count: COD 4 had amazing maps, so I trust Respawn. In actuality, I don't need a huge count; I need great maps that can be replayed ad infinitum. Maps as good as Lockout, Midship, and Crash. Maps that just never get old.
Modern Warfare 2 launched with 16, of varying quality.
I have full faith in Respawn that they will deliver quality over quantity, or a balanced mix of both.