La_maisonBLoodSireOr Valve will develop a way to make TF2 clearly superior
There's no need. Both games will have their strengths and weaknesses and benefit from each other. At the end of the day, it comes down to individual preference.
I'm not seeing how they will "benefit from eachother" from any perspective really. From Valve/Blizzard's perspective they will be thinking of it like a business.