I am actually looking into the future. Notice that I mentioned about a judge being selected. Congress could stall and drag out the process of approving a new justice for months and months. And if the case is heard before another justice is approved, the case could end up in a tie and the result would revert back to the lower court's decision.
But I am glad you are optimistic about Johnson 
The way some of the SCOTUS rulings have gone the last few years before Scalia's death, it demonstrates a very political court. Maybe they aren't ruling based on what a particular party or elected official wants, but what they believe given their ideologies.
If it's a choice between a Liberal-leaning majority and a 50/50 split, I'd rather have an even number.
BTW, there is no mandate for the number of justices other than Congress making appropriations for them. There's part of me wondering if a ruling is always going to be 5-4, then maybe that ruling wasn't necessarily correct. If 6 judges, independent of ideology, can't be swayed to rule the same way, then the argument may not have been all that compelling. Food for thought.
And from what I can tell on here, you're the only one optimistic about Johnson.
