Service Bulletin (SB) 78B, which specifies the requirements for the installation of the modified fuel tanks, with a compliance date of April 2013.
There is a date. The SB actually states end of April from memory.
As the above states, if an operator is using the RHC maintenance schedule, then the SB has all of the teeth it needs.
The original SB for this gave a complete by date of end of next year I believe and it keeps getting reduced by RHC. Under pressure of course.
I'm also not sure if an AD can be issued if a SB is in existence, better people on here can answer that one. It would be an ICAO thing, I'm sure.