That's an unknown for now. It would be daft for Paradox to impose DRM on their physical release when DRM-free digital versions are available - but Namco Bandai did exactly that with Witcher 2 and Paradox's "DRM-free to Steam-exclusive" shift doesn't give cause for optimism.
However in the worst case (of DRM on the Paradox physical release) you could give your friends a GOG code also so they'd have a DRM-free version along with the physical goodies, though that does mean paying twice.
Well, let's take Warner Bros who took over physical distribution and publishing for Witcher 2 (and the upcoming Witcher 3) in North America. The box copy sold by Warner Bros is completely DRM-free and customers additionally get a GoG backup of the Enhanced Version. So it's definitely possible to make a deal with a "traditional publisher" without sacrificing a DRM-free approach. Of course the first deal with Namco was different but CDPR learnt from their mistakes...
The best solution imo for Pillars would be DRM-free physical box version with a serial which also could be activated on Steam. That way both customer "trends" would be satisfied, the Steam lovers and the DRM-free lovers.
Holy...
Didn't know about WB distributing Witcher 2 in NA, but knowing the stance on DRM that the big studios have, I wouldn't have given it a snowball's chance in hell that they would agree to distribute it without wrapping it in 7 layers of DRM. I'm guessing that the part of WB which dealt with it was a long way removed from the area which deals with movie distribution (and is slightly more customer friendly...)