Dortmund has been in the business of buying and selling of players to make profit for for a long time a team that is doing that has nothing to do with winning or trophies that's why you see their team finding it difficult to win trophies yet they don't get affected financially.
For sure they making money and made a lot in the last years with selling players , but mostly they have to sell them because of there higher salary they want.
And on top of that they want trophies but they got unlucky and other teams was better in that seasons.
Guirassy has not yet been sold because they may be planning to groom new set to players so that next season when he's sold the team will still have some good players I believe the team will be getting more profit if he keeps performing well next season.
I dont think that Guirassy will be sold this year (but who knows)
If he can make and play the same as he did in the last one his price will be grow and others will looking to get him.
Would be a loss for Dortmund.