Four years after the Raspberry Pi 4 shipped, today the Raspberry Pi 5 is launching with a much improved SoC leading to significant performance gains.
The Raspberry Pi 5 is designed to deliver a 2~3x performance improvement over the Raspberry Pi 4. The Raspberry Pi 5 features a quad-core Cortex-A76 processor that clocks up to 2.4GHz, compared to the four Cortex-A72 cores found in the Raspberry Pi 4 that only clocked up to 1.8GHz. The graphics are also much-improved with now having an 800MHz VideoCore VII graphics processor over the VideoCore VI graphics with the Raspberry Pi 4. The Raspberry Pi 5 is capable of driving two 4K @ 60Hz displays and features 4K @ 60 HEVC decode hardware capabilities.
Also interesting with the Raspberry Pi 5 is that it features in-house silicon in the form of the RP1 "southbridge" used for much of the board's I/O capabilities. This southbridge should yield faster USB I/O along with other I/O bandwidth upgrades like a doubling of the peak SD card performance. The Raspberry Pi 5 also features a single-lane PCI Express 2.0 interface for improved connectivity.
I think M.2 would require controller of sorts and would consume considerably more power. However nothing is stopping them from implementing flash chip. Even 8GB is more than enough for what device is normally used.
Pretty sure electrically it's just a Mini PCIe slot, which it already has a controller for.
Hm, in that case, M.2 slot would be a nice add, even thought it might be a challenging thing to squeeze in physically.