However, Ginsberg may retire after this year and filling HER seat with a constitutionalist IS a net gain for us. Also possible age outs are Thomas (no gain), Breyer (gain), and Kennedy (gain).
I see Ginsburg and Breyer holding on for dear life. Nothing short of catastrophic health problems will cause their retirement.
Kennedy, however, is a possibility. Apparently, he's made quiet noises about it, and he admires Gorsuch. The appointment may make him more confident in retiring, in which case we get a second pro-gun Justice.
Of course, the issue is more complex than that. David Souter was advertised as a "slam dunk" to President Bush. Many expected him to side with us, but he dissented in both Heller and McDonald.