Sometimes (not often) a country that was once recognized as requiring refugee assistance reverts to a country that doesn’t and the host country withdraws its protection (think the current US action with Haiti, but not quite as draconian). In those cases, the refugees return home. However, since you arrived in April, I doubt thing will have settled to the point the Government if Canada would do such a thing (in fact, I doubt they ever have). So your claim would be processed based on the information available and your basis of claim at the time you applied.
As far as success rate, they are looking at your basis of claim and supporting documents and evidence. If it looks like a valid claim, they take the case (if resources permit), if not they refuse.