It has been known since the start of the season that Red Bull will not be using Honda engine perse, but their own engine. They purchased the factory the formula 1 engines were manufactured for Honda, which in return means Red Bull basically has their own engine factory nowadays, it is still Honda obviously and they hired their staff and all, it is just that the costs will be paid by Red Bull and not Honda, so Honda will not be paying for that factory anymore but will not be getting the profits from it neither, whereas Red Bull will have to pay for it but they will not be paying Honda anymore. It is still sort of the same thing, doesn't really change much if you ask me.
It's just about two big companies that are making achievements and profits for each year, so for a certainty it will be known at the beginning of the year before the race starts because I was also surprised when there was news that Honda would withdraw from F1 which in fact is still questionable.