We have unbelievable depth in D.
Chabot
Jaros
Harpur
All look like they can play in the NHL right now. 2 of those guys are going to be in the AHL this year, and that's more than fine, even if they deserve to be in our top 7. Then you have Englund who likely sees NHL time soon.
Extending Boro, in all likelihood, means for more than a year, and for more money than he's making now. Tying up a roster spot with him, after watching him for the past 4 years and with the 3/4 guys we have knocking on the door already, seems extremely redundant and problematic with regards to actually getting all our best D on the roster.
I have zero problems with tying up a roster spot if it's the 7th D spot. That's a place I don't think prospects with a future should ever be stuck in.
Should we extend Boro though? I'm indifferent. Our coaching staff (both past and present) seem to like him in the lineup, often at the expense of prospects fans think have a future. I suspect that if we do re-sign or extend him, he'll continue be in the lineup over guys we prefer.
What I do know, is we should not do anything until we see how Boucher uses the guys we currently have. As you pointed out, we have depth; perhaps Harpur ends up providing what Boucher likes about Boro, and instead of keep Boro as our #7 we opt to have Wideman as our injury replacement.
In fact, I think we probably have more depth in defensive guys (and Left handed guys too for that matter) with Claesson, Harpur, Jaros, Englund and potentially even Lajoie so it may make more sense to keep the extra Right handed offensive guy who's fully developed instead.