You mean if this would lead to a tied vote? Your guess is as good as anyone's.

Also, the filibuster rule is under discussion at the moment, it's not certain that the rules we know today stand at the time of a Justice having to be appointed. Also, you have to keep in mind one of the Justices would have to die between today and June 2013 for your question to be relevant.

And then of course, there is the recess appointment.