Highly unlikely, though. I think people are expecting miracles from the partnership given previous successes, but even if it's a good engine the McLaren aero isn't good enough to make the most of it. Look at the other Merc-powered cars, they're not even in the same league as the factory cars.
Yes, Merc would still have the advantage of developing around that engine rather than shoving it in like the others, but even so. I would not expect McLaren Honda to be competitive for at least two seasons. After that, who knows?