When/if there is a new Mac Mini with an M2, M1 Pro, or something else, I suggest you give thought to what you use the computer for. That will clarify in your mind whether a new, almost surely higher priced one is worth it compared to the current M1 Mac Mini. Considering the price of the M2 MBP and M2 MBA I think that if a new M2 Mac Mini comes out in the same case with basically just an upgrade from M1 to M2 that there will be a $200 price increase. For some people the slightly faster CPU, GPU, Neural Engine, and RAM will be useful, but for lots of people those things will likely not even be noticeable.
I carefully thought about my usage and decided to buy an M1 Mac Mini 16gb/512gb + external 2tb SSD several months ago.
Considering my computer use I figured out that the M1 Pro, M1 Max, and M1 Ultra offered no benefit for me. All the M1 series have the same CPU single core speed so little to no difference in using Lightroom Classic. Having 4 performance cores and 4 efficiency cores seems to be working well for me. I just do one photo export at a time so exports are already fast. The exports can make use of the GPU and the 8 core GPU seems to work very well.
I sometimes use Topaz programs and the interactive use and exports are fast with M1. Topaz uses the Neural Engine and the M1, M1 Pro, and M1 Max all have the same 16 core Neural Engine so they are all about the same speed. I just process one photo at a time, not batches.
The M1 has the 8 core CPU/8 core GPU and 8 core CPU/7 core GPU versions, but the M1 Mac Mini only offers the 8/8 version. The M2 has the 8 core CPU/10 core GPU and 8 core CPU/8 core GPU versions. Maybe if there is an M2 Mac Mini it will only have the 8/10 version. Assuming Apple just replaces the M1 with the M2 and uses the same case, same ports, etc. then judging by the M2 MBP and M2 MBA the price will likely be $200 more.
Lightroom Classic and Topaz already run fast enough on my M1 so any small increase in speed with M2 would not gain me anything and almost surely not even be noticeable. If a new software version comes along that causes the current M1 to not perform well then my opinion can change, of course.
Here is the basic info for the current Apple Silicon SoCs:
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M2 8-core (4P/4E) 8-core 16-core 100GB/s 8GB / 16GB / 24GB
M2 8-core (4P/4E) 10-core 16-core 100GB/s 8GB / 16GB / 24GB
The M2 CPU/GPU cores are faster than the M1 family CPU/GPU cores and the M2 Neural Engine is faster than the M1 Neural Engine. M2 memory is also faster than the base M1 memory.