First, yes, the new Mac Pro will be able to support 12 cores. Its one of the biggest selling points of the new Mac Pro releasing this month.
http://www.apple.com/mac-pro/
Second, not sure about Avid.
Third, chaufferdevan is completely right. There hasn't been a peep from Blackmagic in recent times about the new BMCC4k. Hopefully this is Blackmagic learning their lesson and they're going to surprise everyone with the shipment and availability of their next camera. However, I'm not holding my breath. Hopefully it arrives sooner than later though!
Good luck with your upgrade! I too am not completely computer savvy, so I hope that someone more knowledgeable than I stops by this thread soon.