Just because Honda is going back into grand prix racing doesn't mean that BMW or Toyota will follow.
As the global economy took a nose-dive a few years back, a whole slew of manufacturers withdrew from Formula One. Within two years, Honda, Toyota and BMW all canceled their F1 programs, either shutting down or selling the teams they ran. With the economy recovering and a new engine regulations coming to F1, Honda saw the time was right to return to the sport. But while recent rumors circulating the paddock suggested they might, both Toyota and BMW have denied any potential return to F1 in the near future.
This is the second piece of news we've seen in as many days surrounding both Toyota and BMW, which are partnering on engine technology and a new sportscar program. But on the race track, the two have pursued different paths since exiting grand prix racing. Toyota has refocused on its Le Mans program, while BMW is focused on DTM. For its part, Honda is said to be in discussions with other teams to supply with engines, but that won't happen for a couple more years at the earliest. In the meantime, Ferrari, Renault, Mercedes and Cosworth will continue powering their own as well as the other customer teams on the grid.