In about 20 years, and not before,
we'll probably have a good idea of exactly what the long-term risks of vaping are. Until then, it's all speculation, and nobody really knows.1
I reckon that it's almost certainly much safer than smoking, but that the risks are unknown until long-term studies are concluded. Since many millions of people managed to stop smoking before vaping was a thing, I'd say that anyone clinging to vaping as a substitute (and insisting that there's NO WAY they could have quit without it) are people who weren't sufficiently motivated to quit smoking in the first place.
1. See also: Brexit.
(, Sun 30 Dec 2018, 23:37, Reply)
I refuse to quit the EU until there's an affordable hipster alternative
(, Sun 30 Dec 2018, 23:59, Reply)