Most news stories about the drama in the valley have either said a few churches wish to remain episcopal or the number five is used. Remain Episcopal itself is currently claiming three: Holy Family, St John, Lodi and St. Anne Stockton. Assuming that everyone who is attending those churches wishes to remain affiliated with the Episcopal Church, that gives Remain Episcopal a probable membership of around 330 (combined ASA of all three churches). The Diocese has an ASA of around 4000. So the Tories in San Joaquin are about 8% of the diocese.
I suspect there are more than that. I also suspect that, five years from now, if you added up the ASA's of the Rebel and the Tory churches, it would be below 4,000. I hope not. But the reality for both sides is that they are older, with fewer children than the population as a whole. Also there are current members for whom the cost of litigation, any litigation will be too high. They will move on and find a church with fewer lawyers.
Unless someone in San Joaquin shows a hitherto undemonstrated talent for evangelism, the numbers will dwindle.
Sidenote: Holy Family has grown since 2004. But, a lot of that growth is directly attributable to people joining it from a church that was closed. I do not expect that growth to continue in the medium to long term.