Thank you. It seems I've forgot the math.\(
H(jw) = \frac{2wj}{4wj+10000}
\)
As w gets very large, the 4wj term in the denominator will become very large as well. It will get to the point where it is much larger than 10000 and it will 'appear' as if the response is:
\(
H(jw) = \frac{2wj}{4wj} = \frac{1}{2}
\)