Hi Michael,
There is no out-of-box solution for this right now.
But there is this feature we are using to change the logo on a page basis as you might see on the home page of the showcase site where the logo is overridden and different from the rest of the site. You can add a page id to the logo name and place it in the theme config folder: eg: /application/config/pixel_theme/logo-dark-1.png (1 here signals the cID of the home page)
Header always checks if a custom logo for the current page exists before picking the main chosen logo.
So, you can use this feature, which is not the most convenient solution. Or use the code for this feature (\theme_pixel\themes\pixel\elements\header.php) and come up with a solution to check the language id of the current page before picking the default logo. Of course the latter solution need a bit of coding,
Cheers,