It'll just mix. Brewers yeasts do not reproduce sexually, so it's not like you can create a new yeast strain by pitching them both and hoping they get it on.
S-04 will most likely dominate the fermentation due to its fast fermentation & high flocculation. When it starts falling it's going to take the US-05 with it. Plus there won't be much left for the US-05 to dine on because S-04 ate it most of it. Cheers!!!