I too hope they sign. Yeah, there will be issues if they sign. It will be a bumpy road as they establish a prelature or some other juridical structure. There will be other issues to work out over time - (whether the FSSP and other Ecclesia Dei groups decide to come under the umbrella, whether Bishop Williamson will be given faculties, etc.) but these are better resolved inside the Church than outside.
And it will be nice to have more Tridentine Masses being offered in full communion with Rome. The spiritual graces will be wonderful.
I may even take in the occasional Tridentine Mass myself. (My family is Eastern Catholic).