TL;DR: A conservative wouldn't change the balance Scalia provided, and a liberal wouild recognize that Heller hasn't actually changed things all that much (but that overturning it might lead to proposals for a beefed-up constitutional amendment that would).
Why the Supreme Court Won’t Impact Gun Rights or the Second Amendment at All – The Atlantic
The Second Amendment has been vigorously protected by the elected branches of government—don’t look for the next Court to change that.
It's not just one seat, though. Ruth is hanging on, but there is always risk when cancer is concerned.
True. The article is focused in particular on this currently vacant Scalia seat.
I thought the concern over an actual constitutional convention should Heller be overturned in some fashion was interesting; I'd not heard that, though the reasoning makes (sadly) a lot of sense.