The Call of Duty: Black Ops Forums have a confirmation from Treyarch that the upcoming installment in the military shooter series will have a dev console, also confirming that there will indeed be mod support after the release of Call of Duty: Black Ops, though the exact nature of this is still not clear (thanks joao). Here's word:

We plan to open the game up for modding sometime post-launch. We do not know yet to what extent you will be able to mod the game. There are some purely technical issues related to engine and internal tool enhancements that do not easily fit the modtools paradigm. We have looked at it close enough to see that it is non-trivial and we will have to pick it up again post-launch. Right now we are completely focused on finishing the game.

And, dev console: confirmed.