I think in the end Watanuki is going to be forced to let go of Yuuko ╥_╥

well this is before the ending of the manga and we know that he waited for her 100 years so.... i dont think so

And we also know that it won't be Doumeki Shizuka that uses the egg, rather it will be his great grandson who will or possibly a future generatkon from that with doumeki's face.