Having returned to MotoGP full-time in 2015 and won the championship with Joan in 2020, Suzuki made the shock announcement part way through the 2022 season that it would be ending its involvement at the end of the campaign.
Suzuki cited financial reasons as well as changing market trends as its primary reason, with the Japanese marque's withdrawal from factory-supported racing having a knock-on effect in numerous paddocks.
Speaking during the Assen World Superbike round on Friday, Viegas said he believes Suzuki will one day return to MotoGP as "they cannot sell bikes if they are not in competition" and is "optimistic" other brands will invest in FIM-sanctioned world championships going forward.
"It's tough because Suzuki left us," he said when asked by Autosport what the FIM hopes to do to attract manufacturers to MotoGP and WSBK.
"I had the occasion to speak to Mr Suzuki himself in Japan, and they said they were going to invest all the money they had in a new type of engine, blah, blah, blah.
"I think they will be back. They cannot sell bikes if they are not in competition.
"We had two very tough years with the COVID, but I think things are getting much better now and I think that new manufacturers will join in both competitions – in MotoGP and [World] Superbikes, which is not easy because the investment in MotoGP mainly is huge.
"But in Superbikes you need to have a very good investment to be competitive.
"But you see now in the Endurance [World Championship], Ducati is joining, which was not the case before. And they have the help of the factory.
"So, I am optimistic but what we have to do to bring them is to have the regulations made according to the manufacturers – not against them, otherwise they will not come.
"So all of this is an interactive system that we are doing all the time with the promoter, with the MSMA, and within the FIM we discuss a lot. So, that's the only way: to discuss and decide."
Viegas added that, in MotoGP terms, it is only missing involvement from Kawasaki and BMW – but currently there isn't scope to expand on the grid's current five brands.
"In MotoGP, we are missing Kawasaki and BMW," he said.
"But they don't want to come, and there's no room for the time being. Maybe Suzuki will come back, we'll see."
