Was just watching some of the Goodwood Festival of Speed rally stage live stream - in the Day 2 coverage they had a good interview with Jari-Matti Latvala, GR rally team boss...
Towards the end of the interview he talks about his rally Celica and the model's history in WRC. I think he lets slip a little nugget about the future WRC car being a Celica - he said "...the Celica won the championship in 92, 93 & 94, so we want to keep the story of Celica alive because the heritage and thinking about the future, is something that we want to bring it, maybe (corrects himself with a cheeky grin!), back in the game in the future."
So my money is on the new GR Celica being the WRC replacement for the GR Yaris in a few years!