In other words, they may huff and puff, but in the end they're not leaving.
In the Episcopal Church, most property is in the name of the bishop, holding for the diocese. The national church will try to claim that the bishops are holding in trust for the national church, but the bishops have a solid argument that the national church is merely an administrative body. It will have to be litigated, but at least by the law of my state, the bishops have a good shot at it.
The denominational HQ of ECUSA is actually organized as a "mission society" with all the dioceses as voluntary participants. Until the 20's or so the Presiding Bishop was actually the senior diocesan until they decided to organize on a corporate approach.
You're right. This isn't a slam dunk in any event. The only one winning this one are the stinkin' lawyers again. There is going to be a fight literally over billions of dollars of real estate and pension fund money.
The Pension Fund is another matter. It's a separate unit. From what I understand, you are vested after 5 years so most clergy could bail.