Nishioka is right now the closest to the achievement, but 2016's potential is perhaps a little smaller than 2015. Don't think we're gonna see so many new faces this time around.
I'm not so sure about that - last year we saw the start of the process of the oldies being pushed out, but mostly by a lot of gen useless finally crawl in (albeit with a fair sprinkling of teens). Also last year relatively few bit runs up the rankings (as we did the year before) - I think we might see a few more of those this year though.
This year I think the generation change process in the top 100 will really accelerate as gen late 90s really come into their own.
Nishioka is an obvious one, but I would also suggest that Ymer, Donaldson, Kachenov, Fritz, Tiafoe, Rublev, Jasika, Halys, Djere, Duckhee Lee, Tommy Paul and several others well within striking distance.
And several in the slightly older group with a chance (among the Australians, Jordan Thompson and JP Smith in with a chance).