The trick is to not treat it like a zero sum game and to realise that to live a middle class life in America/Europe is to live life of luxury that almost nobody in human history could ever have dreamed of.
Well question is how long the structure that enables that life can be sustained. A lot of it is simply inertial from being tech hegemon which makes west price setters, i.e. FX fixers able to leverage indispensable technology to drive up western purchasing power. Once that's gone, when PRC basically can sell you everything the west use to that enables modern development all the leverage is gone and purchasing power will revert towards mean, which for developed countries = down. Things may only decline/contract vs others so fast, but likely noticable amount within a few generations.
