But with minuscule TV ratings on NBC Sports Network the chances of a third manufacturer coming in are slim to none.
"A third manufacturer is absolutely critical," HPD's Roger Griffiths told Autosport. "The long-term sustainability of IndyCar needs more than just Honda and GM.
"When you've got seven or eight cars and you're subsidising them, that's one thing. But when you've got 12 or 13 or 14 and you're subsidising them, that's completely different, and it's hard for all of us to continue to maintain that level of subsidy.
"I would say that through the next two or three years, I don't believe there is any kind of issue.
"But when you start looking at what happens in 2017; is there going to be a new engine formula or are we going to continue to evolve the current one; what are we going to do about 2020 when that comes around… if you want to continue to have competition, it's very hard to keep that going if there is only two of you doing it.
"We don't need five people doing it; just a third competitive manufacturer would be great. A fourth would be wonderful. What it needs is quality."