Saying that, I am fairly sure others have managed to get the 4xMHz MCLK working on XS1 if you need to go this route for other reasons (eg. DAC requirement).
DSD native is easier - the data rate is half of DoP. That will make it easier for sure.
point me to the "others" who have tried?
SOrry - don't have specific links but googline DSD512 xmos xcore etc. gets commercial products and a few forum posts.