He is adorable! I bet you are very excited! You have come to the right place to learn and share about Yorkies! I have learned tons of info here. Besides it is a fun site with lots of wonderful people.
As to the weight of your yorkie -- no one can say for sure. Adult weight can depend on a lot of things, mostly hereditary but not just mom and dad, grandparents and great-grandparents, and so on. There is a quick estimate that you can use 3 times the 8 week weight, or 2 times the 12 week weight will be a good estimate of what hte adult weight may be. Remember though -- just an estimate or better put, a guesstimate. They can fool you and have late growth spurts or stop growing unusually soon. Here is a growth chart that is also a way to guesstimate the adult weight:
Yorkshire Terrier - Yorkie Puppy Growth/Weight Chart - watch us grow Both methods (multiplication and the chart) require that you know the weight of your puppy. So, no way to estimate right now.