Formula E continues to shape up as a major single seater series of the future.

The latest driver to take the all-electric category seriously is Sergey Sirotkin, who will test in Morocco later this month.

"Formula E is now one of the most rapidly developing championships. The competition here is at very high level," the ousted Williams driver said.

Given the involvement by major manufacturers and top drivers, and the direction the car industry and society is heading, series boss Alejandro Agag thinks Formula E is the series of the future.

"We love formula one, we think it's great" he is quoted by Speed Week. "But I think we will be the only motor sport left in 20, 30, 40 years."

Top Formula E driver Jean-Eric Vergne, who also raced in F1, thinks Formula E and formula one will eventually merge.

"In 2030 there will only be electric cars," he said. "Formula one will have completely changed its attitude in terms of electric.

"Today, Formula E is something completely different from formula one, but I sometimes hear that one day the two series could merge, which I think would be great," Vergne added.

"But formula one is the premier class and it will remain that way -- in whatever form."