someone told me existing legs will not be able to be broken down in this cube. they have to be from drops that happen after the patch goes live. This sounds like a dubious claim to me but thought I'd check here in case anyone can confirm/deny.
The reason I'm asking is at the moment I'm collecting sub-standard versions of legs (with bad rolls) with the intention of extracting their affixes when the patch goes live.
Extraction is off a menu or pre-defined as mentioned above. You get what is on the menu after you have made the passive skill available. So legacy affixes will not have be included. I would think that if you extracted an item with a legacy affix, you would get the menu passive skill. If the item is not on the menu as some Vanilla items at level 60 may be, the cube would probably reject it.