Full story: The BBC
Interesting piece on discussions about what is next for engines in F1 cars, and whether the sport should see a return to V10 engines. These discussions make no sense to me to be happening now. The new regulations kick in next season, and so this cannot be a proposal to rewrite those regulations. Especially given the time, the effort, and the cost that the teams have invested:

Yes, a V10 might be cheaper than a hybrid. But the manufacturers have already spent an estimated collective $400m on the new engines. They are not about to throw that away.

That is a ton of money, and as pointed out in the next paragraph:

And a new V10 would require developing, to the tune of hundreds of millions more.

Especially if the goal is to push that development through in a hurry.