This is what I said weeks ago.
Why would Dortmund sell him to Juve in January, unless they feel that it is actually addition by subtraction. Why would they weaken themselves in the Champions League by selling a player whom, according to a lot of people on this board, would be an extremely welcome addition to Juve.
It doesn't add up, it doesn't make sense. Unless they feel they lose nothing in the process if they sell him, irrespective of to whom they may be selling him to.
And that opens up a whole other can of worms.