See current call for TMT Instrumentation White Papers. Deadline for submission is March 21, 2018.
Currently the main instruments foreseen to be operational at first-light are WFOS, IRIS and IRMS. Any other facility-instruments planned afterwards is part of the “next-generation” suite of instruments.
The TMT Science Advisory Committee (SAC) is planning a "soon to be released" call for White Papers for next-generation instrument capabilities. In addition, the next TMT Science Forum, which will be held in Mysore, India from November 7-9 (https://conference.ipac.caltech.edu/tmtsf2017), will be entirely dedicated to forming the teams kicking off the concept studies for the next generation of TMT instruments. Some of these efforts have already started over the past years, which led to the identification of instruments with specific capabilities:
These instrument concepts will be revisited at the TMT Science Forum to be held in India in November 2017. An outcome of this Forum will be to respond to the call for White Papers on TMT next generation instrumentation, which will lead to launching feasibilities studies later in 2018 for all concepts ranked as top-priority by the TMT Science Advisory Committee.