The Oppo F31 series was recently said to be in development as the successor to the Oppo F29 lineup, which was launched in March. A tipster has now revealed the launch timeline and key specifications of two of the handsets in the series — Oppo F31 and Oppo F31 Pro. Both of them are expected to come with MediaTek Dimensity chipsets. The Oppo F31 series will pack large…