Tbh if they didn't learn from last time (vita) it deserves to fail if they're not including a usable microSD card slot. We're at a point where the cat is out of the bag even for the average consumer, when games can be 100GB+, noone will buy it if they screw about with being an overpriced console + overpriced games. The console needs to be affordable, with affordable memory and then they'll make their profit from the games.
When you consider that a major feature for the PS5 was a highly optimized I/O controller for a very fast SSD, I have no faith whatsoever that we'll be seeing SD cards as a viable game storage mechanism. Unfortunately.
This won't exactly be like the PSP or Vita, because it's not going to have its own separate software library. A large part of what held those platforms back was the fact that developers were too busy making console games, but if this just runs PS4/5 titles then at least that part is sorted out.
It's the same as what Nintendo is doing, one software platform for titles that can be played handheld or console.