There is discussion going on here: https://ethereum-magicians.org/t/precompile-for-general-elliptic-curve-linear-combinations/2581
Recently, @shamatar (Alexander Vlasov) has agreed to become the leader of this Working group with the objective of researching and making reference implementation (and test generation) for this precompile (or group of precompiles). I understand that there is also work on figuring out the formula for the gas cost estimation, which is not trivial.
Please message DM him or post here if you would like to join the group, with the thought of what you can contribute and how much of your time you would like to commit.