A newly elected Senate is not bound by any rules of the prior Senate. They can make up whatever rules they want, including no filibusters, reducing the number necessary for a quorum, etc..
In other worlds, if the Democrats win the Senate this November, you can expect to see them hold incredibly expedited hearings on Obama's Supreme Court nominee, and fam through that confirmation before the new President is inaugurated. Totally legal/Constitutional.
Which means we could lose the Supreme Court before the new President even takes office, even if the current Senate GOP hold firm.
A Democrat controlled Senate is not bound by any rules.
The only reason that Harry Reid did not abolish the Supreme Court filibuster when he unilaterally abolished the filibuster of all other presidential appointments is because there were no Supreme Court vacancies at the time. If Scalia had died while the Democrats still controlled the Senate there is no doubt whatsoever that Reid would have unilaterally abolished the filibuster for Supreme Court appointments as well.
So you are absolutely correct that this is yet another reason why the Republicans (RINOs and all) need to hold on to the Senate this election. If not, then in January you can count on every single judicial vacancy (from Supreme Court down to the district courts) being filled by Obama and Schumer before the next President is sworn in.