Ok, so Volta probably isn't going to happen. Instead, based on recent articles, it looks like they might be going straight to Ampere. So if you are planning to buy a higher end next gen Nvidia card then a 550-650w PSU might make sense depending on what tier of card you are planning for.
For what you have RIGHT NOW, or for anything up to GTX 1060, a 450w unit of good quality is fine.
I'd try to stick to Seasonic (Focus, G, Prime, X series), Corsair (TX, RM, HX, AX series), Antec (True power classic, Edge, High current gamer (Only higher capacity models. 520 and 620w are older group regulated Seasonic built units), FSP (Hydro X, Hydro G) and Super Flower (Leadex, Leadex II, Golden green series).