I doubt it, I think Kojima has a whole other look on the DS. He's developing that new rpg game for it. And I believe he'll continue with that series. It looks like a fun game but a metal gear would still be nice on the DS so I hope i'm wrong.
I think sometimes when a publisher/developer has a game they may be forced to sign a contract stating that they cannot and will not develop for a competiing platform. Kind of like how there are games the Xbox has that the PS doesn't and vice versa.
I doubt we'll see a MGS series for the DS, Sony probably has Konami or whomever in a air tight contract.