While the intention to open up the series' regulations was first revealed at the end of 2012, a final decision has hinged on attracting new manufacturers into the sport.
Following Citroen's announcement of a 2014 programme, led by nine-time World Rally champion Sebastien Loeb, the FIA World Motor Sport Council has now formally confirmed the new regulations will come into effect from the start of next year.
The council also confirmed that 2013-spec cars will be permitted to compete, a move AUTOSPORT first predicted ahead of the current season.
That will effectively boost grid numbers given only Citroen and Honda have so far committed to having their new cars ready for the start of next year.
Lada is understood to be prepared to join them, while SEAT insists its new Leon Cup car will not be ready for the early rounds.
BMW said earlier this month that it would likely leave the series should the new regulations be ushered in.
Promoter Marcello Lotti recently told AUTOSPORT that 2013 cars could benefit from a small update package in order to reduce their expected deficit to new-generation cars.
"It could be we have to keep both regulations on the grid," Lotti said ahead of the WMSC decision.
"If the decision is to keep both, it makes sense to allow a small kit for 2014 to improve the performance of the current cars; this is something we decide in the next couple of weeks.
"It could be easy for everyone to upgrade a little the engine, and perhaps find also other improvements that are easy to do.
"This is an idea. I'm no technician - after the technical people decide what the best kit is without spending a fortune, we will upgrade the regulations to improve the performance."
NO CONCERNS OVER TWO-TIER FIELD
Lotti also played down fears that a two-tier grid could hurt the series, saying: "We were in the same position in 2010, regarding the decision to change to a turbo.
"At this time we were optimistic but not sure 100 per cent there was the commitment that all would switch to the new turbo, so we decided to do both regulations, and make a world cup title for [the older specification] cars.
"Conclusion: at the beginning of the year, we had all but one car with the new turbo. Fantastic, but at the time of June we didn't know. This is perhaps what is going on now."
For the full FIA World Motor Sport Council decision, click here
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