Current PC technology churn that makes me reluctant to think about a new PC
My current home computer will be five years old this fall. Five years is a long enough time in the PC world that any number of people would be looking to replace something that old. I'm not sure I am, though, and one of the reasons for that is that I at least perceive the PC world as being in the middle of a number of technology shifts, ones where I'd rather wait and buy a new machine after all the dust has settled. However, I may be wrong about this; I haven't exactly been paying close attention to the world of PC technology (partly because of my self-reinforcing impression that it's in churn now).
The first point of churn is in SSDs. It seems clear that SSDs are the future of a lot of storage, and it also seems clear that they're busy evolving and shaking out at present. We have ever larger SSDs becoming ever more affordable and on top of that there's coming changes in how you want to connect SSDs to your system. It seems quite likely that things will look rather different in the SSD world in a few years. I expect growing SSD popularity to affect both motherboards and cases, although that may be well under way by now.
The next point of churn, for me, is high DPI displays or more exactly the degree of graphics that I'm going to need to drive one, what sort of connectors it will need, and so on. I think the 'what connector' answer is some version of DisplayPort and the 'what resolution' is probably 3840 by 2160 (aka 4K UHD); I'd like something taller, but everyone seems to have converged on 16:9. On the other hand, this may be last year's answer and next year will bring higher resolution at affordable prices. Certainly the hardware vendors like improvements because improvements sell you things. In addition, the longer I wait the more likely it is that open source graphics drivers will support cards that can drive these displays (cf my long standing worry here).
Finally, there's the issue of RAM and ECC. One part of this is that I have a certain amount of hope that ECC will become more widely available in Intel chipsets and CPUs. Another part of it is that Rowhammer may cause changes in the memory landscape over the next few years. There are claims that the latest generation DDR4 RAM mitigates Rowhammer, but then there are also things like this Third I/O paper [pdf] that have reproduced Rowhammer with some DDR4 modules. Worrying very much about Rowhammer may be overthinking things, but there I go.
(I'd certainly like that any new machine wouldn't be susceptible to a known issue, but that may be asking too much.)
(There are other factors behind my somewhat irrational desire to not put together a new PC, but that's for another entry. Especially since I'm probably wrong about at least one of them.)