Why not? Imo people will say oh ps5 coming why upgrade to the ps4 Pro. Or next year they might just say not buying ps4 at all.
Many factors and possibilities why PS4 and Pro will be fine and to a greater extent PlayStation as a whole.
#1 Gaming in general will have evolved by the time PS5 launches. PlayStation will have the upmost variety in platforms for different budgets.
#2 Potentially the could introduce a Pro Slim
#3 Price reduction is almost guaranteed any time after Black Friday.
#4 By the time PS5 launches we could be looking at prices like PS4-$199 PS4 Pro-$299 PS5-$399-$499.
#5 Software and Cross-gen Software will always continue to sell console. This Holiday season is filling up well. The numbers I believe will do great amongst the big 3 gaming companies. Plus 2019 starts us off with RE2 Remake, Kingdom Hearts 3 and Days Gone.