Slasher, TCAS II version 7 can command an RA reversal if the other aircraft doesn't follow it's own coordinated response - but only once. So if the aircraft DOES subsequently decide to follow it's RA (after you've been commanded to change direction), you will only get increase climb/descent commands rather than another actual reversal. That's how I read it anyway!
TCAS III is just around the corner and will allow lateral guidance as well as vertical...
Lancer