It might have affected domainer to domainer sales on forums like this. All the money being poured into new gtlds, would have been poured elsewhere. But I think it has also helped. All the money being poured into second rate extensions, that could have easily been buying good domains in the Aftermarket. In a way I kind of like them because it keeps newbie domainers off of Namejet bidding up .com.
Now if you look at the last 6 years reported sales of DN Journal, I look at the 100th reported sale, you see it was steadily going down, then started going back up again in 2014, when new gtlds first started coming out.
$81,000 - 2010
$74,333 - 2011
$65,000 - 2012
$55,000 - 2013
$64,499 - 2014 - going back up, 0 new gltds
$78,500 - 2015
And those are mostly .com sales. Confusion, one big cluster f**k, just leads people back home.
So no, I don't think it has affected .com end user sales just because on some of the stuff I posted elsewhere. 99%+ of top 500 internet merchants are on .com. Most new startups still go to .com. People still see .com all day long, even the youth new gltders like to bring up. Serious businesses understand it's just easier with a .com. It's not something they'll ever have to explain to people.