Originally Posted by TheOOB
They have not yet released any sort of multi classing rules, but I can pretty much guarantee it won't work like it does in 3e. My guess, It'll either be something like 4e where you can kinda sort get other class features, or like 2e where you can have a sort of dual advancement type deal.
Actually, they briefly mention you can multiclass like 3E, pg 7 of the new Class PDF under Warlocks: "Unless you have spellcasting from another source:", how you are getting another source unless you multiclass?
So it proves we have 3.5 version to me.