Oh, Mobile DDR5 can certainly spec higher. Unfortunately, in everything I've seen, Rembrandt's OEM spec will be limited to 4800.Actually Mobile LPDDR5 should come in at 5500 if not 6400 bps. Apple M1Pro chips already support LPDDR5-6400.
It should be half decent 1080p gaming. Steamdeck is a good preview. You will most likely need to turn down settings.
But AMD has shown they are pricing to what the market will bear, so I expect they will be expensive, and a long wait until all the laptop OEMs are saturated until you can buy them for desktop usage.