It will truly be a knife through the heart if Dembele leaves. I want to see it happen, before I believe it, though, reliable media reported that he wouldn't leave no matter what this summer just last month.
If he leaves, then the board would edge closer to a vote-of-no-confidence as the transfer-policy + keeping Valverde would be truly retarded.
Getting Neymar back and selling Dembele would be the biggest facepalm in a decade.
On the other hand, if the board manage to keep away from retarded instincts, then getting De Jong + Griezmann is a very good window. Depending on the sales it could be close to great.
For example selling Coutinho + Rakitic + Suarez would free good cash and big wages, which are a very big problem now.
1) Puig + Alena + Vidal could fill out the gap for Rakitic.
2) Griezmann could fill out the gap for Suarez.
3) Dembele and Malcom could fill out the gap for Coutinho.
If we then sell Malcom we would need a new back-up for the attack, one with speed.