When God wanted to deliver a message to the world He used several different applications. From using nature (such as a flood followed by a rainbow), to using fire (such as a burning bush) the Lord delivered His messages. The way God used to reveal to us His directions along with allowing us a peak into the future was most often done through people, otherwise known as prophets, messengers of God.
The Old Testament contains many books written by prophets. Books such as Daniel, Isaiah and Jeremiah. From a chronological order, the prophet Malachi was the last prophet in what is now a canonized version of the Old Testament. The question here is a two fold question. Has God communicated His desires and will for us since the days of Malachi and was Malachi the final prophet God used.
Some people believe that the prophet Malachi was the last time God delivered His message to us. That is simply not true. In-between the timelines of the Old Testament and the New Testament are around 400 years. During that time God saved the Jewish people from some things. What comes to mind is the story of Hanukkah also known as the Feast of Dedication.
God manifested Himself by using the Holy Spirit to guide the Maccabees through many battles which eventually gave them the ability to retake control of Jerusalem and the temple. God's message was clear. In keeping with His past practice, God would not allow the total destruction of the Jewish people and for the time being, wanted them to continue the substitutional sacrificial system that had been instituted by Mosaic Law.
Some have even went as far as to compare Malachi's prophecies to a death bed confession by God. God was not dying and Malachi's message should not be compared to a death bed confession unless you believe that God has remained silent for over 2000 years. Malachi is simply one of many prophets God used. Even today, God has a way of touching our hearts and allowing us to know that He is there. God will never die and continues to guide many people each day.
God promised to give us a New Covenant in Jeremiah 31:31. If you believe Jesus is the promised Messiah then you believe that God instituted this New Covenant through Jesus. If you don't believe in Jesus, then you still believe that this prophetic New Covenant is still to come. Either way, you must believe that God did not finish communicating His will through Malachi. God's message through the prophet Malachi is not a death bed confession.
The New Testament also contains a book classified as prophecy. The Book of Revelation, revealed to us through the apostle John, written during his exile on the island of Patmos around 96 A.D. This prophetic book gives us further insight to the writings of Daniel, Zechariah and other end time prophecies.
Jesus was among other things a Jewish prophet. He foretold about things to come. Some prophecies came true shortly after His death like the destruction of the temple in 70 A. D.. Other prophecies have not occurred yet, but believers in Jesus as the Messiah believe that some day they will when He returns.
Jesus has been viewed by some as not being a biblical prophet because everything He said has not come true yet. However, this is also true for Jeremiah, Isaiah, Ezekiel, Moses and other prophets who prophesied about living in end times and the Messianic Era. For more on this please read The Prophet Jesus.
Moses predicted that someday God would send a prophet even greater than he was (Deuteronomy 18:18). Ask yourself this question. If Jesus is not the fulfilment of this prophecy and Malachi is the final prophet then where is the prophet that will be greater than Moses? For more on this prophecy please read A Prophet Greater Than Moses.
The Talmud teaches that the words written by its writers have now taken the place and even supercede what the Old Testament teaches. For more on this please read Did The Talmud Take The Place Of The Torah?
The Talmud teaches that there had been twice as many prophets as the number who left Egypt (over two million), but only those whose messages were for the future generations were recorded. This count was 48 male and 7 female prophets.(1)
The name Malachi has been translated as messenger or angel.
1). Megillah 14a (www.faqs.org/faqs/judaism.FAQ/06-Jewish-Thought/section-12.html)