Unless we have injuries to deal with I don't really see the need to buy a Pedro replacement in January. I don't think it's ever the best time to buy players. Clubs are less willing to sell due to needing to find midseason replacements, and we'd have to worry about finding new signings who aren't cup tied either.
We have Messi and Neymar who will play the vast majority of games as neither of them seem to like being rested or even subbed off. As backup for them until January we have Sandro, Munir, and Rafinha. Then once the window opens we'll also have Arda and Aleix who can both operate well in wide attacking roles. Yes, Turan can play in midfield, but I think at least until he gets up to speed Iniesta and Rakitic will still be the starters there. And yes, Vidal can play at right back, but we have Dani there, and Sergi Roberto has been doing well so far.