Sure, there is always the possibility of new physics being discovered. But we know A LOT about the universe, and the fact that we can explain so much about how things work, from the atomic to the galactic level, without any kind of a time-stable identity being necessary does suggest that we shouldn't hold our breath hoping for one to be discovered.
Also note, a hash or a mind in a higher-level universe is exactly a transcendent soul: it transcends what we call physical reality (or it transcends 'the simulation' in that story). Just because it's framed in scientific concepts doesn't make it any more or less scientific than Brahman or Christian souls.
Yes, we know a lot, but we don't understand consciousness or even why the universe exists at all. You are probably right, there is unlikely to be a necessity for a "time-stable identity". But who knows, as Lord Kelvin said 1901 “there is nothing new to be discovered in physics now"!
Also note, a hash or a mind in a higher-level universe is exactly a transcendent soul: it transcends what we call physical reality (or it transcends 'the simulation' in that story). Just because it's framed in scientific concepts doesn't make it any more or less scientific than Brahman or Christian souls.