You’re assuming anyone else wants to breakaway. Most of the breakaways have already happened, Diocese of S. Carolina (which just for information sake does not mean the entire state of S. Carolina) being one of the the largest. But that 2015 decided court case was the summation of a years long court battle that began roughly around the time of this article you posted was written (2012). Since then the only other decision I’m aware of was the Falls Church, VA court decision in 2014 which again was the summation of a years long court battle (and that one went the other way with the assets being assigned to the ECUSA.) I highly doubt the decision is going to embolden anyone who hadn’t already withdrawn.
And yes the ECUSA has seen a decline both in recent years and in the last half century, but it’s actually not really any different than mainline Protestantism in general in that regard (or Catholicism for that matter when immigrants aren’t included). The ECUSA has seen a 49% drop in membership in the last 50 years. But that’s in line with other mainline denominations which have seen between 27% (ELCA) and 67% (Disciples of Christ) drops in membership. The other big mainline denominations, Presbyterian Church, Methodist Church, Reformed Church, United Church of Christ, have all seen drop offs in that range. Even some non-mainline churches like the Lutheran Church Missouri Synod has seen a 20% drop in that 50 year time. And churches like the SBC which have grown overall in that time are starting to see losses in more recent years. All of Christianity is hurting in the west other than the Seventh Day Adventists, non denominational Churches and if you want to count them as Christian the LDS Church by some accounts is holding steady but even they are shrinking according to others. I’d point you to
this:
http://www.pewforum.org/files/2015/05/PR_15.05.12_RLS-00.png
I’ll agree with Little Sheep here. The ECUSA is an oft used target because many in more conservative leaning denominations disagree with their stances on issues, but fact is the ECUSA is not unique in it’s struggles right now.