Yeah, that's a possibility. Islam could probably have taken over the rest of the Philippines, and it's not far from there.
Yes its is possible since the Bruneians are holding parts of the Philippines and the rest are either in their influence or raided by them.
It is a possibility not an assurance.
Both Sulu and Brunei are not good in spreading religion. In OTL, Both Mindanao near sulu and Sarawak surrounding Brunei were not predominantly Muslim. For Mindanao it never was. It had to be the British/Malaysians who made North Borneo/Sarawak Islam.
The more likely scenario is Luzon reverts back to hindu/animists while Visayas remains Hindu and resistant to Islam. Or Luzon becomes Chinese. Luzon during this time period had more Chinese than supporters of Islam, Sultanate of Manila, Brunei. just to get an idea, The Spanish during their 1570 invasion could muster the same amount of Christians vs the Rajah Suleiman can muster those warriors that can fight for Islam. This is after almost one hundred years of Islamic rule. While the Chinese within the same time period, can muster tens of thousands in Manila albeit angry traders/migrants. Or any Chinese invasion force even just pirate(would be multiple times greater than what Brunei and Sulu can muster).
If we are going to make Luzon Islam, without changing anything how Brunei or Sulu runs things, both Brunei and Sulu must keep on holding those areas until any similar OTL 20th century tech. Brunei and Sulu are not good at spreading religion, annexing and assimilating conquered lands.
It means Brunei empires needs to survive any invasion from Chinese, which did happen within the same time period. Limahong(Chinese pirate/couple of years from Legazpi invading Luzon) did invade the Philippines which Brunei/Sulu wont have any answer to. Plus whatever Chinese migrants/trader living in Manila. Of course, any rebellion by any hindu/animist local who still views Brunei/Sulu and Islam as invaders. Down the line You still got Koxinga. The common factor of stopping any of these Chinese invasion/pirates was the modern tactics/firepower of the Spanish.