This isn't regarding the referendums on the issue taking place this year, but does anyone know if there any chance that Marijuana is legalized nationwide via Supreme Court?
Not going to happen. Even if the federal laws against marijuana end, the states are perfectly within their rights to ban it.
One famous example: Prohibition ended in 1933, but 18 states kept their state Prohibition laws on the books and were completely valid. The last of these was Mississippi, which had Prohibition as a state law until 1966(!).