Sanguinius' foresight definitely hasn't been retconned out, it's just a very different ability to Night Haunter's and has a far less important role in defining his character and behaviour. Night Haunter's foresight only ever covers the worst possible future, it just so happens that he himself is always endeavoring (if not always consciously) to create that future. Sanguinius' visions on the other hand are less specific, both in that they can cover any potential future and they aren't as clear visually. Sanguinius also appears to only receive his visions in dreams while Night Haunter's often occur in painful seizures.
This means Sanguinius is gifted vague dreams of things that might occur while Night Haunter is cursed with visions of horrible things that he believes will occur.
"Look into my eyes, and see your death."
"Let them hate, so long as they fear."