Frank De Jong again? That guy had good chances of going to England teams, especially to Manchester United but he chosed to play in Champions league because Manchester United is playing in europa league. In short time he will also see himself in the Europa League 
. If he sees any good offer by January he may leave.
In the previous transfer window, he has an opportunity moving to Man United but he refused it since Barcelona still didn't pay all his salaries. As far as I know, the reason was about the salary, not about Man United not playing in UCL. Sure, he finally will play in Europa League also because Barcelona seems hard to qualify for the next stage in UCL. . If he sees any good offer by January he may leave.Frank De Jong is no longer a key player for Barcelona, he spends much time on the bench now. No doubt that he will leave Barcelona if there is a top club makes an interesting offer. Barcelona also needs fresh money to balance the players' salaries. So, it will be good both for De Jong and for Barcelona as well.
Frank De Jong was benched by Barcelona, and it didn't work out well. De Jong is extremely upset about not starting matches and may leave FC Barcelona if things do not change. Leaving would be better for him, but he refused earlier after making so much controversy. The upcoming January transfer window is a great opportunity for him to move to a better place when he gets enough playing time and he doesn't make any excuses for not moving.
Seeing De Jong warming the bench for Barcelona during this season makes me quite sad. He had the option of moving to Manchester United, but I believe that that transfer would have been very detrimental to his career. Let's just take a look at the current situation at Manchester United right now, shall we? There is no doubt that even Casemiro is not playing well with them at the moment. As such, I think if he had transferred to Manchester United, his career would have been jeopardized. In the next window, he ought to look for alternative options that might be ideally suited to his needs. His play style would be well-suited to the double pivot that Bayern plays, and that is one of the reasons why I think Bayern would make a wise option for him.