They've already confirmed about three free DLC packs. Some include more missions, more heists etc. why don't you do a bit of researching before you just open your mouth and spew out ignorant "facts". As GI Joe says,
Knowing is half the battle!
1. If the DLC packs make up the 700 missions then unless they are free that is false advertising as they discussed the GTAO months ago as having 700 missions. No mention of DLC helping to accumulate that was brought up however do provide a source if I am wrong.
They're not really DLC in the traditional sense where you pay and get some more game to play, they're more just updates that add new stuff to the game. The heist missions in the DLC will count towards the 700 missions. The DLC packs they've announced will be free.
Rockstar said they had 700 missions ready to go and that around 500 would be in the game at launch. They also said GTA Online would be always evolving and new content would be coming all the time. Just don't think of it the same as COD's DLC more like a staggered launch of the initial round of content.
Do you even know what DLC means? Guess not.