According to this news more than 50% of people would be middle class: http://www.economist.com/node/13063298, the news is from 2009 so maybe now it would be around a 48% or the like considering there's a world economic crisis, considering that news true.
However that seems to be the opposite than for example this other news: http://www.theguardian.com/money/2006/dec/06/business.internationalnews. I mean, if the 10% of population has the 85% of resources we would need an impressive technology to make a good amount of that people middle class, we have much better technology that centuries ago, but still I feel we'd need one that would make sci-fi films look like prehistoric times.
If that weren't enough this other news shows that there more rich people: http://money.cnn.com/2014/10/29/news/economy/billionaires-oxfam/index.html, and if there's more rich people obviously there's going to be more poor people.
I don't know very well what to think, what I find more possible is a 25% of people being middle class or higher and rest low class. But well, I'd like to know from accurate data how exactly is the world wealth distributed.