More importantly, it's one thing to say "I prefer this new tech/resolution/gadget" and another to claim "how can you work like this?" (Where "this" can be "without a mac", "without a mechanical keyboard", "without a 4K monitor", "without three 4K monitors", etc).
Software is developed successfully without any of those. It's not only not an impediment, it's not like a sort of martyrdom either. So no, it's not time to upgrade that monitor.
Someone else in this thread commented that for many devs, their gadgets are a proxy for actual skill. It's easier to show you have a 5K monitor "like all hackers should" than to actually be a good developer.
It should also be cheap enough now, and at some point fabbing a 200+ PPI display will cost the same as an older one, it won't make much sense to keep making the lower res displays anymore (like it doesn't make sense to fab 32MB DIMMs anymore).
I just disagree that it's "time to upgrade your monitor", or that the current tech is bad or makes it hard to be productive.
The bigger issue is that, like we've been doing for the last 40 years, a cutting edge 2X display should eventually become the new 1X display, while the former 1X's become obsolete. This makes building software a bit easier, even with resolution independence, it is difficult supporting more than 2 generations of display technologies (e.g. right now we have 100 PPI, 150 PPI, 220 PPI, even 300+ PPI at the bleeding edge).