Question: If a saintly miracle occurs, can it establish the possibility of another prophet?
Answer: No. A karāmah is not prophethood. The finality of prophethood rules out a new prophet or an independent revealed law; a miracle claim cannot overturn that principle.
وَإِنَّهُ خَاتَمُ الْأَنْبِيَاءِ
He is the last of the prophets.
Follow-up: What is the central measure when considering a saintly claim?
Clarification: Faith, piety and adherence to the Muhammadan revelation remain central. An extraordinary event cannot become an authority above revelation.