One more question. Do you mean parole or probation?
If it is Parole and he finishes on December 28, what he wants is at least possible. If he was on probation, then it's very unlikely.
After a felony arrest, the state has 5 days from his arrest to present the case to the Grand Jury and be ready to vote the indictment. If they can't meet their obligation, the defendant must be released on that case. With a parole hold, he would not get out, but there would be $1 bail placed on the new grand larceny so he'd get credit for the time in.
An exception to the release would occur if the defense lawyer asks the lawyer to hold off voting the indictment in order to cut a deal, or if your friend wishes to tell his story to the grand jury, which it does not appear he's doing. It looks as if the lawyer has told the judge he will not testify and the case has been transferred to Supreme Court for the next date, by which time he will either be indicted or returned to criminal court on the misdemeanor
If reduced and he doesn't take an immediate plea on the misdemeanor (it will be a jail offer, since he's already in) and a dollar bail is set upon reduction, once his parole hold is up he can get out, fight the misdemeanor and try to get a non-incarceratory offer.
Rehab will not be possible as he will have been detoxed in jail already. But misdemeanor drug court would be an option. For that matter, though, time served may be an option too. It's going to depend on the facts of the case.
If it's indicted, he's a predicate felon, and he'd be looking at a few years in. As a predicate, he won't be eligible for drug court, though he could get treatment in-house.