Some people speculate how Blockbuster could have wiped Netflix from existence while Netflix was young. Similarly, I believe right now the time window is still open for Quora to remain dominant. Because blockchain technology is almost completely open source anybody, including Quora, can adopt it. If Quora was to do something relatively soon such as create an official ERC20 token and start monetizing their questions and answers then they would maintain the dominance they already have in my opinion. Beyond a certain tipping point that may occur, much like Blockbuster, no matter what Quora would do they might not be able to hold on to their base support. It's hard to say ahead of time when this tipping point might occur if it ever does.