They have embedded the Kronos, SV1, and Nautilus sound engine into the Pa5.
Er not so quick...
first of all there isnt just ONE sound engine in the KRONOS but many - and of those the only one that applies here is the ROMPLER one. The modelling engines - whether synth, hammond, EP , strings, etc are ONLY in the KRONOS and NAUTILUS ranges.
And as to what has been brought into the PA5 - its the addition of STREAMING from NAND "Disk" for certain big sample size instruments - pianos chiefly - from KRONOS.
But as I understand it - that streaming ability only applies to the ON BOARD factory sounds Korg have added to PA5 from Nautilus. Because of technical limitations and the size of the internal SSD ( NAND ) storage - there won't be any means to expand the PA5 with 3rd party (Huge sample size) libraries sold for the KRONOS/NAUTILUS family. The internal NAND SSD isnt that big and theres no ability to stream from external SSD because the circuit and bus tech wont support it. There does seem a question mark as to how big exactly the internal SSD ( NAND ROM ) actually is - and how much would be free to install extra (huge gigabyte ) libraries in future - but my bet is that it wont support much in the way go gigabyte size libraries - if any -
So although its great to see some Nautilus instruments in there - engine wise and expandability wise - certainly disk capacity wise - this isnt NAUTILUS "Lite"
So I like so many am waiting with baited breath to see what Yamaha do with the next gen Genos. And crossing fingers they do the "right thing" and include finally a USB output that supports multichannel digital audio.