according to Red Bull Racing advisor Helmut Marko "Red Bull racing will leave formula 1 if the
collaboration with Honda fails"
after a collaboration of 12 years with Renault, Red Bull Racing will have Honda as their new engine supplier for next season. In the last twelve years with Renault they had some very successful years, Sebastian Vettel winning the championship four times in a row between 2010 and 2013. But after the new engine regulations in 2014, the relationship between Red Bull Racing and Renault was starting to cool down because Renault has not been able to catch up with Mercedes and Ferrari in terms of engine power and reliability. Despite all promises made by Renault and already the fifth season with the new engine regulations they are still miles behind Mercedes and Ferrari, all this resulted in Red Bull choosing for Honda next season.
With Ferrari and Mercedes refusing to deliver engines to Red Bull Racing, Honda is the only option left for Red Bull Racing, but I am sure they collected all the necessary data about the Honda engine from Red Bull's little sister Toro Rosso to justify this decision.
I sincerely hope this new deal with Honda will work out well because Formula 1 can not afford to lose 2 more teams.