It wouldn't be a cap dump. Looking at the Sens roster, There's only 4 dmen signed. Lajoie and Brannstrom COULD both be full-timers next year but even then the team needs another dman in the veteran role Hainsey played this year.
Sens will have Zaitsev, Chabot, Reilly, Wolanin essentially guaranteed spots, with Boro almost certain to get one, too. Zub seems like he may very well sign with us, and I suspect he steps into our top 6 immediately (so, if you're counting, we're up to 6). Hainsey might be re-signed, and then Jaros, Brannstrom, Lajoie, Thomson and Alsing will all compete for a spot. I would rather Russell than Hainsey, but the Sens aren't exactly itching for DMen. Young guys will get lots of opportunities.