There's a solid chance Labour won't get a majority and will rely on either confidence and supply, or a full coalition. There are very few precedents for a party going from as low as 202 seats at one election to a majority government at the next (it happened in 1945, but only because the last election in that case was 1935 and rather a lot had happened in between).
Labour have been very clear where they stand on electoral reform. If we're going to get a change to the voting system, it will only be because Labour were forced into it by the Lib Dems in a hung parliament.