The fact that timing and process impact each other doesn't mean they're part of each other. You might as well be saying cancer is in part a matter of death.

Yes, if the Supremes rule in the same direction at the 6th Circuit, and not in the direction of the other couple of Circuits, then their decisions will be overturned and the bans directly addressed by the cases in question will still be in place. That won't be all of the 20+ states affected since some of them were struck down as subsidiary rulings which SCOTUS isn't directly addressed and might require further court or legislative action to stay in place or be put back in place but it's the gist.

Why now? Because now is when it is actually before the Court. Yes, there was an opportunity to issue an injunction. Yes, it is extremely odd that one wasn't issued. A stay until the next level of appeal is decided is pretty much routine and everyone was surprised when it wasn't granted. You can think it suggests something all you want, but you'll be whistling in the dark, since the stays are regularly issued even when the Court's future decision permitting exactly what is being stayed is pretty clear. Another possible explanation is that the original decisions against granting stays came before an earlier decision by SCOTUS not to hear the appeals from the first few sets of Circuit Courts, back before there was a disagreement among them. If the Court was pretty clear it wasn't going to take the appeal then not granting a stay made sense, and continuing to do so with the couple of requests that have trickled in since they were forced to reverse and grant cert after all could be a matter of consistency.

Kennedy is the most reliable swing voter. There's a lot of chatter that Roberts might swing but. . . the basis I keep hearing is people citing things like ACA. It's the regular delusion that politics=jurisprudence. The fact that he has swung left on a couple of rulings which have nothing in common with this issue, from a legal perspective, is not telling. His questions during the oral argument were more bipartisan than most of the others but as I said earlier, making predictions from how oral arguments go is really chancy. Oral arguments and their questions from the justices these days seem to be almost meaningless. There certainly isn't a sign that he's likely to swing visible in the earlier decisions. He is less predictable than the others because he's a "political" judge, one of the justices who was nominated on the basis of a high profile as a lawyer and politically rather than from extensive experience on lesser benches, but I don't think that's really enough to predict he might swing. It'll explain a swing in hindsight but it's not enough to do so now.