From 60's to 70's, the real GDP growth per capita of the world fluctuated about 3%. Since then, it fluctuated about 1.8% or somewhere around. (I mean, the average would be about 1.8% since 1970.) I found this trend from the data provided by Google public data. Is there a consensus among economists that the real GDP growth per capita of the world will be stable or gradually decrease in the future?
I don't think there is a consensus about this. In 1980s and 1990s, growth theorists have tried to endogeneize the technological progress in growth models, that shows a "balanced growth path" (in which economy grows at a constant rate in long distance.) So, we can say that economists don't want a decrease in GDP.
But note that there are some people who support the idea of "degrowth". You can find a definition on Wikipedia.