She is a cutie! I would defo be worried about her leaving her mum too soon though, I got my GSD at 6 weeks and I truly wish I didnt get her so soon. Pups learn so much much from their litter mates and mum. My GSD totaly doesnt get it if another dog growls at her, Im really lucky that she such a softie with other dogs. It hasnt always been that way with people though, she is the best dog ever but has been constant hard work up untill she was about 4, shes now 8.
Be very carefull with your yorkie an new dog being together, even just playing normally she could really hurt the little one. I have a Chihuahua and he is always crated when mine are left alone, anything could happen when your not there with them. Ive heard so many storys of little dogs getting hurt and even dying just from playing with a bigger dogs.
You should definalty get involved in dog training with her when shes older, staffy's are such clever dogs and people need to see how brilliant they can be. A friend of mine competes in agility and obedience with her staff, and she is amazing! its so nice to change peoples opinions of them
Good luck when you get her! bet your so excited!
...Sorry about all spelling mistakes, in work trying to type very quickly so havnt had chance to check it all