will MIDI Controllers like korg nanokey be supported?

There will be no MIDI support in the first version. "camd.library" for MorphOS must be done first. Then assuming Poseidon can handle these Korg devices, they will be supported.

is it going to be a shareware software or maybe there will be a trial version?

The current plan is, it will be sold by APC&TCP. There is a demo version planned, if they want trial version, I will prepare it.

can you estimate when it will be released?

No. Too many variables...