The word for "Islands" can also be translated as "Coastlands."
Isaiah was a prophet who operated during the divided kingdom, after Solomon, when the ten northern tribes of Israel split from the two southern tribes of Judah and Benjamin. The ten northern tribes had more or less joined Judaism to the pagan practices around them. Isaiah was faithful to the God of Israel and exhorted the northern tribes to return to the God of their fathers.
The Old Testament contains much symbolism and common objects are often used to reference other things. For example, in Matthew 13, Jesus says that the kingdom of God will be like a mustard tree and that birds will make a home in it:
**He proposed another parable to them. "The kingdom of heaven is like a mustard seed that a person took and sowed in a field. It is the smallest of all the seeds, yet when full-grown it is the largest of plants. It becomes a large tree, and the birds of the sky come and dwell in its branches." (Matthew 13:31-32)
Trees are often used to represent mighty nations. Birds are often used to represent gentiles, non-Jews. Jesus is telling his followers that the Church will become a mighty nation and that the Gentiles will dwell there. Similarly, being "under the fig tree" was a euphamism for being a student of the Scriptures or a follower of the Law of Moses.
**Nathanael said to him, "How do you know me?" Jesus answered and said to him, "Before Philip called you, I saw you under the fig tree." Nathanael answered him, "Rabbi, you are the Son of God; you are the King of Israel." (1 John 1:48-49)
In the case of the islands/coastlands, these are usually a euphamism for those who are far away from Judea, far away from God and the center of worship in Jerusalem. It probably has less to do with an actual location then it does with the state of one's heart toward God.
We have to remember that the Jews were not a seafaring nation and so islands were difficult for them to reach without assistance. They were farmers and herders, and in some cases fishermen, but the coast/sea/islands were not places with which their culture readily identified. These would seem to most Jews to be far off, distant places, kind of like us saying "Timbuk Tu". So the short answer is no, the PHilippines is probably not what Isaiah is talking about.
The Bible was inspired by God but written by men who used their human skill to communicate to us exactly what God wants us to know for our salvation. Whomever wrote Isaiah surely never dreampt of such a place as the Phillipines. And that is really the whole point of scripture, why God gave us Scripture - our salvation - so that we can be saved. Prophesying about the Phillipines really does nothing to save someone in Africa, or in suburban Atlanta for that matter.