As long as English is the common language, the power shift is limited
Language is the main carrier of knowledge, while innovation can be ignited via communication. As long as the common language is English, the communication among Asians is restrained, so is the innovation. Without innovation, Asia can not lead the world.
The Asians, especially the Japanese, are struggling to learn English, because their mother language is so different. What makes matter worse, it is hard to have a common language for Asians themselves. Some will argue that Mandarine (Chinese) will be proper as common language, because Asian languages, especially Japanese, Korean and Vietnam languages are influenced a lot by Chinese. However, the fact is that the Koreans and Vietnamese already stop using Chinese characters.
In addition, I do not think the day will come when other language replace English as common language. Therefore, the power shift to Asia will be limited.