Unless Sony wants to go completely crazy and use Leviathan instead of Kraken on the Pro, if there'll even be a Pro. Only time will tell, it's way too early to tell and the PS5 hasn't even released yet.
Couple reasons why Sony probably went with zlib (from zlib's website):
- zlib is designed to be a free, general-purpose, legally unencumbered -- that is, not covered by any patents -- lossless data-compression library for use on virtually any computer hardware and operating system.
- zlib's memory footprint can also be specified fairly precisely.
Remember that zlib is on-chip in the PS5, and it's buffers for decompression are completely on-chip. No CPU, or main-memory is needed. This is huge, and accounts for why faster SSD's on the PC show little to no performance gains when loading games, because, the loading part is small part of it. It's the decompression of assets in memory by the CPU cores, which take up the most time.
With the PS5, main memory, and the CPU cores are not impacted, and thus, initial game loading will be much faster than any PC. Because the CPU's are not needed for decompression, thus also allowing assets to be decompressed in real-time as your playing the game, and the regular game code and memory will not be impacted at anytime with this overhead.
Any Pro model that comes out, will have to use the same compression, or all compressed assets for a game will have to be duplicated to support both compression standards. I can't see that happening in the same generation.
Oodle data compression algorithms are not free, and we have no ideal, what the cost is in number of transistors to implement on a chip, or what size the buffers have to be for decompression.