Assuming we continue with a 3 man midfield like this:
---RCM--LCM---
------CDM------
It looks as though the plan is for 1 of Henderson or Can sit at the base of the midfield in the #6/CDM role, and I'd imagine Dahoud would compete with Wijnaldum and Grujic for the #8/box to box role with Lallana or Coutinho occupying the other, more attacking role in the 3. We're quite fortunate in that all of those players are capable of playing 2-3 positions though.
Henderson (CDM, CM, RM)
Can (CDM, CM, CB, RB, LB)
Dahoud (CDM, CM, AM)
Grujic (CDM, CM, AM)
Wijnaldum (CM, AM, RW, LW)
Lallana (CM, AM, RW, LW)
Coutinho (AM, LW)
Media and 'ITK' buzz seems to be that we have had scouts at every game watching Dahoud this season, and that we will definitely be making an offer for him in January - supposedly around the 25m mark but I wouldn't be surprised if it took more than that.