Hello and welcome to the forum.
I'm afraid it's much too early to tell.
The ferry timetables are usually published around late February to early March for the summer season so don't expect any firm details before then. Once they are finally released they are still likely to change, particularly early and late season so keep checking!
The best place to find information is the ferry operators' own websites:
http://www.12ne.gr/en/ for the main (mostly) every day crossings and
http://www.bluestarferries.com/ for the (currently) twice weekly "big boats" from Athens to Rhodes and back, passing through Symi on the way.
Andy Ward is our travel expert and he keeps up to date with timetables, producing his own version to cover crossings to and from Symi which we publish here on the Symi Chat forum as soon as they are available. Keep an eye on the 'Noticeboard' section for the latest information.
His regular travel blog at
http://symivisitor-accommodation.com/blog/ always has the latest news on everything to do with travel to and from Symi.