The FIA has taken the first steps to allowing in-season power unit development for 2016 after an engine manufacturers meeting in Geneva today.
In-season development will be a huge boost to both Honda and Renault as they attempt to close the gap to their rivals.
The meeting also agreed that manufacturers can field more than one spec of engine next season, opening the door for year-old units to be used, as was the case with Manor this year.
However, both proposals require rule changes and still have to go through the process of being formally drafted and then unanimously agreed at the F1 Commission, and then ratified by the World Motor Sport Council. At the moment, no date has been set for the next F1 Commission meeting.
Today's meeting was attended only by the FIA and representatives of the four engine manufacturers, with Toto Wolff (Mercedes), Maurizio Arrivabene (Ferrari), Cyril Abiteboul (Renault) and Yasuhisa Arai (Honda) joined by their top engineers.
The other teams, who would still have to agree via a unanimous vote on any changes for next season, were not present.
As things stand, the 2016 FIA Sporting Regulations specify that there is no development after engines are homologated by the usual February 28 deadline, and the rules also specify that only one specification can be used during the season.
The potential for use of older-spec engines may open a door for both Red Bull and Toro Rosso to stay in the sport.