I have a good idea for creating a good incentive for playing more maps in a rotation. Activision could create a 'stock market' like situation, where maps have various point multipliers based on their popularity. A popular map might have a lower 80% multiplier for your xp, while a map thats usually skipped gets a higher number, like 150%. And have the numbers change daily or hourly to make things interesting. you could even do it for weapons too. Noob tube is lower xp over a more skilled weapon, but I can see problems with the weapon multiplier in TDM with teammates dying more frequently with low percentage weapons, but it's something worth throwing out there.
It would also be nice to honour loyal COD players by releasing old maps from other COD titles... old DLC or old launch titles, because right now if your playing the most current COD, your maps are only good for a year or less.