Assuming some of these perspectives have changed? Looks like the perfect deal to me. He's starting to produce at Hart levels, and if he does so for the next 4 years we will have gotten that production at bargain basement prices, while shedding Benn and Seguins contracts. If he keeps it up, there's no issue offering him a huge deal.
I also think part of it is we should know what we have with the likes of Johnston and Stankoven who look like tracking a similar trajectory (amazing if either somehow turn out this good lol). If they turn into genuine NHL superstars, then we should have some flexibility with what we might want to do (not saying we'd let Robertson go, but lots of things can change in 4 years).