Heres some more rumors, all speculation but some food for thought at the same time.
1. All the weapons from the original are coming again.
2. 3 maps from the original are coming back with a few noticeable tweaks here & there.
3. There is a total of 16 maps including 3 from the original.
4. 20 new weapons will be added to the inventory & the most noticeable are the FAMAS assault rifle, HK PSG-1 sniper rifle, MP7 sub machine gun, AA12 fully automatic shotgun, MG4 LMG and the .44 magnum revolver.
5. Multiple attachment perk has been added which allows 2 attachments to be added to a weapon.
6. The Single Player Campaign is predicted to last 7+ hours.
7. Co-op Mode has been added.
8. A new Alien Terrorist co-op mode is also added with details still unknown.
9. The multiplayer is set to have 4 new modes above the original modes.
10. A new CLAN system & TOURNAMENT system will be added.
11. The PS version of the game is set to have Dedicated severs provided from SONY [Xbox Servers status still unknown].
This is from cod6.org