Does anyone know if and when Tech Comm Suite 4 will be available?
Nope (& even if we did know, we would be bound by NDAs not to tell ;>)
New versions of TechComm products historically have been released on a 1.5-2 year cycle. They also seem to come out about one-quarter to half year after a major Acrobat release.
FWIW, FM10 and TCS3 were released in January 2011.
Otherwise, as Jeff says, those that do know, can't say...