nobody could expect Koltsov to come into Vancouver and replace Salo... that's not likely to happen.
What Koltsov does is replace his salary slot on the pro roster.... replacing Salo will take more than anyone dman to do, but hopefully this season all 3 of Bieksa, Krajicek and Bourdon develop a bit, and hopefully improvements from those 3 and Koltsov can replace Salo's loss.
I also don't expect to see Salo back after this year... he's considerably underpaid for what he brings, and chances are that he'll get a huge raise on his next deal. With the canucks already committed $7 mill to Ohlund and Mitchell, in front of Luongo's $6.75mill deal, it's unlikely the canucks find the room to add another $3+mill dman, and Salo will get nothing short of that.
I was disappointed to learn that Mitchell signed a NTC in his contract as well... if Salo has another season like last year, I'd rather have him here at that price and ship Mitchell out in a year... it'd make perfect sense as well, since Allen, rumoured to want to return, could be a cheaper replacement on the left side.
But with the way it's shaping up - Salo will be replaced on the right side by Koltsov, joining Krajicek and Bieksa in a year (barring other trades), while the left side will have Ohlund, Mitchell and Bourdon. I don't see the need in bringing in Allen next year with that left side, and I wouldn't risk signing him to play his off-side, which he hasn't played well on before, and hasn't even played there since his days with Baron.

