People have spent however many years since the release of the last pi suggesting improvements. It's announced today offering basically everything that people were asking for, and you are already planning for the next one?
<captainpickardfacepalm.gif>
Huh? I'm not allowed to hope for future improvements?
I'm very happy for RPi4 SD improvements. Until now, RPi has had same lacking ~20 MB/s SD performance from the start. AFAIK, this is the first time ever there's been any hardware improvement in this regard.
I've had a microsdxc card with 90 MB/s reads and 80 MB/s writes since early 2014. Some current cards can read & write more than 250 MB/s, so there's still room for improvement.
As 95-99% of all RPis boot from (micro) SD and use it as primary storage, I'd say SD performance is a rather fundamental (often ignored) aspect of RPi performance.
Doubled, so I guess around 40 MB/s. Still a far cry from fastest SD cards that can both read and write over 250 MB/s. Hopefully RPi4+ will improve on this. :-)