“It means the end of the Catholic Church on earth prophesied by someone recognized as a saint. Suppose then that prediction is considered infallible”
Sorry, but you suppose wrong. In the Catholic Church only the Pope can proclaim something claimed to be infallible, and only under a certain circumstance known as speaking “ex-cathedra;” meaning “from the chair.” Speaking ex-cathedra is a formal undertaking, and does not apply to everything a Pope may say. The term is easily researched. You might do so rather than suppose about such things.
(I don’t believe in ex-cathedra infallibility, BTW.)
I assumed the writings of saints were considered part of the faith. Guess there's a loophole.
Thanks, but that's not completely true either. Ex cathedra Papal decrees are infallible, but so are solemn definitions of general councils (e.g., the canons of the Council of Trent). Also, the Pope and the bishops together can teach infallibly even when not gathered in a council.