Does iPad mini 4 also feature the new and faster 2nd-Generation Touch ID sensor featured in the iPhone 6s?
Apple's iPhone 6s website has a section about Touch ID on the Technology page. It says:


  Touch ID lets you unlock your phone and make purchases with Apple Pay simply by using your ﬁngerprint. It uses highly sophisticated algorithms to recognize and securely match your ﬁngerprint. And the improved Touch ID sensor detects your ﬁngerprint even faster than the previous generation.


By comparison, the iPad mini 4 has a whole page about Touch ID, but it never references a previous generation that's been improved upon. That leads me to think that the iPad mini 4 doesn't share the iPhone 6s's Touch ID 2 technology.