David Oastler tested the new A64000 to see if it had some overheating issue. Luckely he encountered no issues at all.
Photogaphyblog tested the A6400 and the conclusion is rather mixed feeling:
Ultimately, the new Sony Alpha A6400 is a frustrating camera – outstanding in some aspects, most notably the AF system, good in others, but mediocre in some key areas by today’s high standards. Overall, it’s still a good bet, especially if you shoot a lot of moving subjects, but it also could potentially have been so much better…
Testing the real time tracking AF on the Sony A6400, videos and samples (Enthusiastphotoblog).