If history is any guide, Israel has never released any one with more than few months left in his sentence unless it is in exchange for it's POW. Palestinians can release Shalit now and wait for 9 life sentences for the last prisoner to be out or can hold on to him and get their prisoners out in few months or few years. Getting prisoners out of Israeli jail has been, is and will be with one sole method, in exchange for Israeli POW.
Several injured after Jerusalem protest march against Al-Aqsa restrictions dispersed (Haaretz)
from the article: Army of Islam says Shalit now solely under control of Hamas