“I expect them to be much closer next year,” Tost told Formula1.com. “I am convinced that they have the resource and know-how to close the gap.
“If not then the FIA has to look into the [engine development] token story so that everybody who is behind gets extra development freedom until we have parity. But as I just said, I am sure that those behind will catch up, at the latest by 2017.”
Tost maintains, though, that parting ways with Renault at the end of this season would be the right thing to do. Toro Rosso are instead hoping to return to Ferrari power for 2016, rekindling their previous relationship of seven years which ended in 2013.
“If you take into consideration that we have paid a lot of money [to Renault] and didn’t see progress as we had expected, then there must be the question of why not go back to Ferrari - a partner we know and who also makes sense logistically,” Tost commented.
Without Toro Rosso and sister team Red Bull, Renault could be left with just their own works team - expected to be formed from their takeover of Lotus - on the grid next year. Tost agreed this could hamper the French manufacturer’s progress, but insisted it is none of his concern.
“I have no idea what business plan Renault has worked out,” he said. “I am also not interested in what they plan to do, but history has shown that it is good to have at least one customer [team] to have a reference. But that’s their game.”
The seven Mercedes- and Ferrari-engined teams have claimed 909 world championship points between them this season. That compares to 194 for Renault power with Red Bull and Toro Rosso, and 19 for Honda with sole partners McLaren.