CAPTCHAs, which are often seen in web applications, are working under the assumption, that they pose a challenge which a human can solve easily while a machine will most likely fail. Prominent examples are identifying distorted letters or categorizing certain objects in images.
Neural networks are threatening this approach, as they are capable of solving problems that are easy for humans and difficult for classic algorithms. Especially with the incredible results modern CNN architectures have achieved in image recognition during the last years, the established forms of CAPTCHAs won't be able to distinguish a human and a machine using a neural network anymore.
Is this the end of CAPTCHAs as we know them or are there evolved versions available or at least in the making that still pose a challenge to modern neural networks?
Clarification: I am talking about challenges that are feasible for use in web applications and do not have an unjustifiable impact on usability.