I don't think he will get bigger than 9-10 pounds. Keoki is still so small and is 9 pounds right now ( but it's because he has been getting too many treats at his grandmas house and is now on a diet) his normal weight is 7.5 but I LOVE him sturdy - he suits my lifestyle and i like that he's tough and sturdy
I would not worry- there is NO WAY your furbaby will be 20 pounds