According to the Federal Bureau of Prisons, Osiel Cárdenas was transferred from ADX Florence to USP Florence High (located in the same prison). He will now be able to interact other inmates. I'm not entirely sure when this happened, but if it was recent, it may have been done because El Chapo may be taking his place soon. Cárdenas will be out in about six years and before the age of 60. I think we can expect for his conditions inside the prison to improve as the years progress and the government prepares for his reinstatement into society.
Note: Osiel Cárdenas was Mexico's most-wanted drug lord from the late 1990s till his arrest in 2003. He was the top leader of the Gulf Cartel and the founder of Los Zetas, their former paramilitary group. He was extradited to the U.S. in 2007 and is expected to be released in 2025. Few details are known on what boiled down in his trial, but many suspect he collaborated with authorities for a soother sentence.
I think it's unlikely. U.S. authorities have convinced him to cooperate with them by making appeals to self-preservation. If he gets involved in the drug trade again, who knows, maybe they'll revoke the visas given to his family, take more money from him, and release him to Mexico upon the conclusion of his sentence (which will turn him into a big target). He pretty much provided the U.S. with invaluable information on how Los Zetas and the Gulf Cartel operated. People want him dead back home.
I also don't think Mexico wants him back. They pretty much extradited him because he was causing a lot of disruption in Altiplano prison (organizing riots, ordering murders, planning hunger strikes, in addition to running the Gulf Cartel). I think he understands his glory days are gone.
Cárdenas has 5 years of supervised released after 2025. A few bloggers here have said that Cárdenas may return to Mexico after his sentence. I don't personally think he will. But hiding in the U.S. won't guarantee his safety forever. My two cents...