Stosur has been a top player for about 2 years. Give it some time. I am sure there are a few juniors just starting out who will try to play this game. If they fail, then it's because this technique is too difficult for women to perfect (in which case Sam gets a lot of credit), just like how the Williamses's GOAT serving didn't inspire a wave of great servers. Players just couldn't serve like that, no matter how hard they tried.
Players didn't have the athleticism and technique to execute the forehand-slice game of Graf immaculately either (not that Spirlea and such didn't try) or the flair to hit Henin's one-hander.
If by revolution, you mean imitable change, and if that is a key criterion for greatness/etc, then Evert wins hands-down by popularising the double-hander. Yet she consistently played second-fiddle to Navratilova in the second half of their careers.
I came across an article a few days ago which quoted either Stephens herself or someone close to her, saying that she WAS focussing more on trying to generate topspin rather than trying to produce as much raw pace as possible (though up til now, it doesn't look like that approach is bearing much fruit, seeing as the amount of spin she's creating atm is innocuous compared to Stosur).
But anyway, in answer to Williamsova, I'm assuming topspin will become more prevalent in the women's game simply because, as I said, the women's game has always followed the trends of the men's game, and heavy use of topspin has become commonplace in the men's game in recent years
But, just because Stosur and perhaps in the future Stephens, among others, will have pioneered this particular thing, that does not in itself mean they would be better players than Serena, or any other past great players, nor does it mean the monstrous flat-hitters of Serena, Venus and Sharapova would not hypothetically be able to beat the topspin players that will be dominating in 10 years' time.