According to a court issued summary of the ruling:
Today's decision resulted from a U.S. Supreme Court order that the Kansas Court reconsider its earlier denial of an appeal by Matthew Limon, who received a 17-year prison sentence based on a consensual relationship with a co-resident of a group home. Limon was 18 at the time of the offense and the victim, 15. The presumptive sentence for the same act involving members of the opposite sex would have been 13, 14, or 15 months imprisonment.
The Kansas Supreme Court "ordered Limon to be resentenced as if the law treated illegal gay sex and illegal straight sex the same, and it struck language from the law that resulted in the different treatment."
Given that he was sentenced in the year 2000, that he had not prevailed in his appeal prior to reaching the U.S. Supreme Court, and that the conviction itself doesn't appear to have been contested, just the sentence, it seems likely that he will be released since credit for time served should exceed the maximum possible sentence he can face now. If he had not prevailed, he could have been in a Kansas prison for another twelve years, possibly less some allowance for good time or parole consideration.