Teac announced the successor to the 503 series during IFA 2017.
The UD / NT-505 (the latter will be Roon Ready and MQA compatible) that uses two AKM: AK4497 (DSD22,5 MHz and 32bit/768kHz).
I have the NT-503 at the moment and it does a great job (except not being Roon Ready), but I will probably upgrade to the NT505 when it’s released.