Only God knows, of course, whether or not your uncle was sincere when he claimed he was committing his life to Christ. But if he was, you can rejoice that he is now in heaven.
You see, it's never too late for us to turn to Christ -- because God has promised to forgive anyone who honestly turns to Him in repentance and faith. Do you remember the two criminals who were crucified with Jesus? One mocked Jesus and refused to believe He was the Savior -- but the other turned to Jesus in faith and trust, believing that Jesus could forgive his sins and give him the gift of eternal life. He was only hours away from death -- but Jesus still welcomed him. He said, "I tell you the truth, today you will be with me in paradise" (Luke 23:43).
At the same time, the Bible repeatedly warns us not to delay turning to Christ. Life is uncertain; an accident or sudden health crisis may intervene, and we may not have an opportunity to turn to Him. In addition, as we grow older our hearts often become hardened and insensitive toward God. The Bible warns, "Seek the Lord while he may be found; call on him while he is near" (Isaiah 55:6).
Most of all, when we delay turning to Christ, we miss the years of joy and peace He wanted to give us, and the blessing of knowing He is with us. Make sure of your salvation by giving your life to Christ today.