Yes Gen. Alexander is still speaking at Black Hat. I'm not sure that DT has the influence inside Black Hat that he once did. I would be interested to see how that talk goes down, but then BH has never been about "hackers" in the way that DEF CON is
There appears to be a distinct effort to separate BH and DC this year, there is less speaker overlap compared with previous years, attendance to BH doesn't get you in to DC like it used to, etc. This is probably UBM (owners of the BH brand) trying to protect their revenue.