I feel like if KG and Ray are both gone, Pierce may be too. He was a part of many mediocre teams before the big 3 and if those guys leave and aren't immediately replaced by All Stars, he may not be too excited to come back. It may not be retirement, he could discreetly ask Danny to try and send him to a west coast contender(LAClippers, Houston, Portland, Golden State-depending on how they're offseasons go). With that said, I hope he's back and retires as a Celtic when he's ready.