Switch games don't even have a 64GB card yet, and PS5 is supposed to make 4K a standard? Nah. These cartridges would be hella expensive and no developer would want to use them. I think Sony is making something that can appeal to the Japanese Market with a PSP3 type device that plays on the TV much like a Switch and they'll release it worldwide as well. If Sony can actually support the thing, it could see amazing success and be cartridge based.It'd probably be based off of newer tech than the Switch, and this is probably why people feel the Switch refresh will be in 2019 and will feature a power boost.
We should know more by mid 2019, if info doesn't start leaking before then.