In one of the news program that I watched on the youtube (not sure which one now), there is mentioning of the J-18 being an upgraded program of the J-31, whereby its outlook are very much the same as the J-31 (not sure how true that is, since no one actually see a J-18 thus far).
However, as seen, even up till now, most new aircraft (in prototype stages) are powered by Russian engines, although China's engine are very much matured now, and breakthroughs had occured pretty much in all areas, however, the VTOL/ STOL engine might be a totally new area to venture into is totally untouched by the CHinese at this present time, so how mature would that technology actually be?