Which camera to get in 2026?

Here's a list of all full frame MILCs released from 2013:

| Year-| ---- Sony ---- | ---- Nikon --- | ---- Canon --- | - Panasonic - |
| 2013 | ------α7------ | -------------- | -------------- | ------------- |
| ---- | ------α7R----- | -------------- | -------------- | ------------- |
| 2014 | ------α7S----- | -------------- | -------------- | ------------- |
| ---- | ------α7II---- | -------------- | -------------- | ------------- |
| 2015 | ------α7RII--- | -------------- | -------------- | ------------- |
| ---- | ------α7SII--- | -------------- | -------------- | ------------- |
| 2016 | -------------- | -------------- | -------------- | ------------- |
| ---- | -------------- | -------------- | -------------- | ------------- |
| 2017 | ------α9------ | -------------- | -------------- | ------------- |
| ---- | ------α7RIII-- | -------------- | -------------- | ------------- |
| 2018 | ------α7III--- | ------Z7------ | -------R------ | ------------- |
| ---- | -------------- | ------Z6------ | -------------- | ------------- |
| 2019 | ------α7RIV--- | -------------- | -------RP----- | ------S1----- |
| ---- | -------------- | -------------- | -------Ra----- | --S1R---S1H-- |
| 2020 | -α7SIII--α7c-- | ---Z6II--Z5--- | -------R6----- | ------S5----- |
| ---- | -FX6-----α9II- | ------Z7II---- | -------R5----- | ------------- |
| 2021 | -FX3-----α1--- | ------Z9------ | -------------- | ------------- |
| ---- | ------α7IV---- | -------------- | -------R3----- | ------------- |
| 2022 | ------α7RV---- | -------------- | ------R6II---- | ------------- |
| ---- | -------------- | -------------- | ------R5C----- | ------------- |
| 2023 | ------α7cII--- | ------Zf------ | -------R8----- | -----S5II---- |
| ---- | ------α7cR---- | ------Z8------ | -------------- | -----S5IIx--- |
| 2024 | ------α9III--- | -----Z6III---- | ---R1---R5II-- | ------S9----- |
| ---- | ------α1II---- | -------------- | ---C400--C80-- | ------S5D---- |
| 2025 | ------FX2----- | -----Z5II----- | ------R6III--- | -----S1RII--- |
| ---- | ------α7V----- | -----ZR------- | ------C50----- | --S1II-S1IIE- |

Everyone has their own answer based on their own unique needs.

For me, having owned the a7iii for 6 years now, I'd say there is no point in looking at the newest bodies.
I primarily shoot family and parties. 24MP are sufficient for that. The AF is mostly on point. IQ is superb, as good as the newest cameras. I rarely fill my buffer and 1 battery lasts usually around 5 hours.
So the decision is ultimately not needs based, but wants based.
Going by my needs I'd simply pick another a7iii or an used a9. They are similarly priced (used a7iii ~850€, used a9 ~1000€) and the high-speed readout is nice to have.
My second choice would be an used A7IV. The better AF and slight MP increase are good things to have. ~1500€.

I think we are truly spoiled at the moment with the vast amount of outstanding cameras that can literally do anything. AF, dynamic range, shooting speeds, even lens selection is really not an big issue on any of the platforms. In the past every camera launch was exciting because of the big improvements. Companies would leapfrog over each other. But now we have figuratively hit the ceiling.
The only way things can go now is that bodies will include more and more advanced video features and keep pushing sensor readout speeds - things that most photographers in most circumstances don't care about.