Currently Mercedes, Ferrari, Renault, and Honda supply engines – both to their own premier teams (Red Bull and McLaren for the latter two) but also to other teams like Williams, Sauber, and Toro Rosso. Because the new turbocharged V6 hybrid power units cost those four suppliers so much to develop, they're charging their customer teams big bucks – around $20-30 million per season – to provide the engines. These costs are much higher than the $10 million or so it used to cost to purchase a V8 engine under the previous regulations.
Ecclestone figures it's time to bring in another supplier who will not run their own team and not play favorites, but will supply engines to private teams at a lower cost. There are already a number of potential suppliers under consideration. One of them is said to be Cosworth, which has a long history in the series stretching back to 1963. The British firm stepped back between 2007 and 2009, returned in 2010, and dropped out again after 2013.
The development could be of particular benefit to Red Bull, which has been unable to find an engine supplier and could be forced out of the series as a result. The team has long been powered by Renault, but that relationship has grown sour. And the other three engine manufacturers have not been forthcoming in offering an alternative arrangement for the team.