Monsmartphone reports that while Mango will add 16 new supported languages, users will need to buy new devices to access these.
While this will not be relevant to most people, if Monsmartphone is correct those who are buying devices in unsupported countries at present should not be relying on the Windows Phone 7.5 update to correct the language issues.
On the other hand, if a company like HTC is officially selling the handsets, as they do in India for example, I would expect buyers could very reasonably demand HTC provide a ROM update containing their supported languages once these become available.
Read more at MonSmartphone.com here.