Boedker to me fits exactly on the level of Soda in terms of being a key, although maybe not "core" contributor to the team.
Soda got 5 x $4.75 which some thought was an overpay at the time but looks pretty solid with how he has been able to contribute.
Mikkel is going to be 3+ years younger than Soda was last off-season (he's 4 years, 2 months younger overall). That's going to add a significant premium. Add in escalating contracts summer after summer and I'd say $5.5 x 5 is the minimum you are looking at if he absolutely loves it here and wants to stay. Eating up prime sub-30 years costs more.
Of the quality wingers on the market this summer - none of them (Okposo, Lucic, Ladd, Eriksson, Radulov) are going to come cheap in terms of contract. Obviously Okposo types are way outside our rang...and given his season, I'd say Loui will be too even though he'd be a brilliant fit...and I'd much more trust giving a long term deal to 26 year-old Boedker than older guys whose physical style could lead to complete breakdowns in the near future (Lucic, Ladd types). Radulov, as has been discussed here for over a year now, is the real wildcard.
Take care of Barrie and Nate first obviously but keeping Boedker as well would be a real, real nice feather in the cap for this off-season.