Modeling has come a long way, and some of the high end ones really do sound great. What nobody has been able to reproduce is the feel of a great tube amp running hot.
Even the Kempers don't have that organic magic, where you actually feel the amp working together with the guitar and your hands as one, a single living thing. You feel it through your fingertips.
Maybe someday soon modelers will be able nail that part of the tube mojo too. If an when that day does come, though, somehow I doubt it'll be Fender that does it.