Couple of thoughts here. I don't know of any tech solution that addresses this yet. I looked on Launchpoint and didn't really see one.
Really the best way to do this is segmentation and use of snippets, but the question is how do you get your segments. If I had to solve for this today with little to no budget, this is what I would do:
1) Either craft a CTA + form in Marketo or use a survey tool that displays inside the Marketo email (I believe Decidedly delivers surveys in email).
2) Create one email for each of the languages you intend to support and send your audiences the language you think they prefer
2) Add a "Preferred language" section below the content (CTA or Survey)
2.a) If they select an alternate language, either take them to a landing page or trigger a second email with delivering the content in that language
2.b) Capture responses from people who want a different language and use it to define their segments
4) You can delta out those who prefer the default language based on opens who didn't ask for a different language
You may also want to consider a data enrichment service that has data points that key you in to preferred language if available. Even things like social cues, what language are they using on twitter, etc?