The number I saw on Switch 2 game cartridges is 400MB/sec, which is significantly slower than internal storage or even SD Card Express.
You're not likely to get much faster than that without the cartridge costing even more. Cartridges are all fun and games until they get too expensive and someone (usually the consumer) has to pay the overhead for their cost.
The irony of course is the main advantage cartridges had was it used to be the fastest storage speed available, nowadays it's the slowest. Got people begging to pay a premium so they can have the worst possible experience, lol.







