"Then we will decide if there is still potential development in the existing engine, or whether we need to consider a new development in order to reach Mercedes' standard," team owner Dietrich Mateschitz said this week.
Renault, whose other F1 customers are Toro Rosso, Lotus and Caterham, have reason to be worried.
"We know that Red Bull makes high demands of us," said the French marque's engine boss Rob White, "but I am sure that we can meet them."
Switching to the V6s produced by rivals Mercedes or Ferrari can be ruled out, Honda is not ready to consider servicing customers, and Red Bull's links to Volkswagen are considered wide of the mark.
Another rumour is that the team could build a bespoke 'Red Bull' turbo engine.
"Nothing is impossible," Dr Helmut Marko coyly told Germany's Auto Motor und Sport.
Correspondent Michael Schmidt even has some details of the potential plan.
He said Red Bull already plays a major role in the production of the power unit batteries. And the 'Renault' turbocharger is actually derived from APC Pankl, an Austrian technology collaboration.
The internal combustion engine and motors would be built at AVL, an Austrian company located not far from the scene of this weekend's Austrian grand prix at the Red Bull Ring.
AVL, the world's largest independent powertrain development company, hit the headlines recently when reports of a secret 'rolling road' pre-season test with a Red Bull-owned Toro Rosso took place at its impressive Graz facility.
Schmidt continued: "Infiniti would contribute a portion of the budget and may contribute knowledge about electric motors from the parent company Nissan.
"It is planned that the engine will also be called Infiniti."