I think McLaren shoot themselves in the foot with the switch from Honda to Renault after three years of development.The Honda PU have been reliable in the latter half of the season, just down on power. With the $$ that Honda will now put into TR team, they will move up the Grid for sure next year.
Renault, having PU units for three Teams, have lots of data/feedback, and maybe able to develop their PU faster, but that is not helping them currently, I'm not to sure that they will improve drastically next year...but we'll see.
I still have faith in Honda and their engineering abilities.....
Bram