Also, ACS 4x (tcl) won't be replaced by ACS 4x(java), it will live side-by-side. aD has been working on client sites with ACS 4x (tcl), for instance.
The real break comes with ACS 5. Just as ACS 4 signified a large restructing and rewrite of the ACS 3 toolkit, ACS 5 will be a significant rewrite once again. Read Malte's (aD Germany) comment in the thread mentioned above.
