Is what they say about the randomized guild quests and stuff real?

yes, todd says that the random quests generator would add quests like... for the dark brotherhood, they'll randomly assign you assassination missions (after you complete their scripted quest line)

http://www.wired.com/gamelife/2011/11/skyrim-infinite-quests/

Is it going to be just DB and thieves guild?

im going to assume no, those are the two guilds that todd pointed out, but im going to assume its across all guilds

The article http://pc.gamespy.com/pc/elder-scrolls-v/1212015p1.html seems to indicate it works for everyone, even some shop keepers and crafting people like alchemists.