on the face of it, this seems a rather glib assumption. If Charles, or any other Mary Modena offspring, are being raised anglican, that's going to change the dynamic immensely. They accepted Mary and Anne, they'll accept an anglican Charles, especially since he'll need a regency, and it will be ensured that non Catholics are in charge of that regency. IF King Charles is forcing the Mary kids to be raised anglican, the entire immediate line of ascension is going to be anglican. If Charles is the only male, the line is Charles, his kids (which aren't going to be born for a while, and when they are, if he's anglican, it's likely they're anglican), Mary (anglican), Anne, then any other surviving Mary girls.
all the Mary children prior to '87 died before they came of an age to be taught a faith. King Charles, who died in '85, made Mary (Hyde offspring) and Anne to be raised Anglican. It's likely he does the same for M o M children. This puts James II as the only catholic outlier, and he's dead.
Edit: oops confusing this thread with the one about James and Mary dying in '87. Still, if Charles is anglican, it does change up the dynamics. If he's forced to convert on King Charles' death, that's another story.