In the event that Israel refuses, potentially as JohnBoy says, because they will not want to make the unity government/ Hamas look reasonable. The world, including the Shalits, could judge then who was being intransigent. Regardless of spin, a reasonable deal is the right thing to do, so lets hope both parties do so.
Woman moderately wounded by firebomb thrown at her car in north J'lem (Haaretz)
from the article: Egypt pushing Hamas to soften stance on Shalit deal