spent some time playing with import settings, here is what I found:
= iTunes can import and play (limited by your hardware) WAV files up to 24 bit / 352.8 kHz ⚠
= iTunes can convert these files to Apple Lossless without any transcoding up to 24 bit / 352.8 kHz.
= iTunes can convert Apple Lossless files back to WAV without any loss up to *16 bit* / 352.8 kHz. In "import settings" choose "automatic" or "custom and auto for sample size / rate". So the only problem left is transcoding 24 bit content to 16 bit (without any warning).
= when converting to WAV, in "import settings" you can finely select the sample rate up to 48 kHz: 8, 11.025, 12, 16, 22.050, 24, 32, 44.1 and 48 (actually this gives the wrong impression that 48 kHz is the maximum rate). Since it supports rates at least up to 352.8 kHz it should include the following options too: 88.2, 96, 176.4, 192, 352.8 and probably 384.
@ed2345
thanks for your suggestion I will send this as feedback to Apple.