Who do you think will not vote on major issues?
Alito. He's a slacker. Also he wasn't around for the arguments before the court so he didn't vote. If it was going to be close the court might have brought the lawyers back in and reheard the arguments.
At the SC they hear arguments but don't rule immediately. There are a bunch of cases lined up (this one is from December I believe) also pending votes that Alito hadn't heard.
I'm not suggesting they won't vote, and on core issues such as abortion rights, etc. Ginsberg/Stevens will vote as they always have. It will be on the issues such as emminent domain, partial birth abortion, etc., important but borderline issues when it comes to voting along philosophical lines, that I think this scenario of 8-0 votes will play itself out more often.