Slimming World have released a statement on these (will see if I can find it). They haven't confirmed they're syn free, not all of them anyway. Some are, some (using the syns calculator) aren't. If I can find the statement thing, I'll post it for you to see.
The cynic in me says that they won't all be free because SW will want to protect their brand and sales of their own meals, which is fair enough, when really they could be syn free.