think the burden of proof is on you to show that we still have prophetic writings today. Why do we need more prophesy? What in the Bible is lacking?
The scriptures are not lacking. They are all they are intended to be. But the scriptures teach that God gives some in the church the gift of prophecy to edify the body of Christ. This is a true teaching of scripture. The scriptures are not lacking because the teaching of the scriptures are true.
Didn't the Spirit inspire Paul to write: "All Scripture is inspired by God and profitable for teaching, for reproof, for correction, for training in righteousness; so that the man of God may be adequate, equipped for every good work" (1 Tim. 3:16-17).
How does this argue for no more prophecy?
Notice the scriptures are given so that the man of God can be fully equipped, but the passage does not say that the scriptures are all one needs to be fully equipped. you can give a soldier a gun so that he can be fully equipped, but he still needs a helmet. If a man has the scriptures and not the Spirit, or love, or grace, he is not fully equipped. We need the things the Bible teaches us we need to have. Having what the Bible says we need to have is not a threat to the importance of the Bible.
Also, if you are trying to argue that the Bible is all we need from this, keep in mind that 'scripture' at the time is smaller than it was now, so you would be implying that we do not need what was written after this verse of scripture.
Btw, not all prophecy in Biblical times was recorded in scripture. (See Is all revelation in scripture thread for list of examples.) Some of it, though true, was not included. So why should all of it be in scripture today. Prophecies today are not given by people who knew the 12, so if they are written down they do not meet the tests for cannonicity.