statistics for Wikipedia show this clearly. Total traffic based on our current methods of collecting data show an overall growth of eight percent.
When you compare the traffic for the English Wikipedia, without mobile traffic it would have decreased by five percent on a year on year basis. With mobile traffic its reduction is only one percent.
When you compare these two screens, it shows that the overall growth in traffic is an additional three percent because of mobile traffic.
Mobile traffic in the bigger languages is doing really well with a 109% growth on a year on year basis. English is the biggest language and its growth of 80% suggests that other languages have at least the same potential and therefore deserve proper attention.
WebFonts. Input methods are different anyway so there is plenty of work left that will ensure that you can do MediaWiki in any language on any device with equal ease.