It will be interesting to see where he is sent. The nearest Federal facility with a sex-offender program is in Seagoville, TX (near Dallas); about a 6 hour drive from the home where Anna lives.
That one is low-security, which is the most likely level he would be assigned. There is also a medium-security facility that houses such offenders that is located in Marianna, FL; that one is about 4 hours from where Anna's parents live. Those would be the 2 closest to allow family to visit most easily, but I wonder if, given the level of enabling the family has done, if it might be decided to deliberately put distance between him and Arkansas in order to make visiting him difficult. The maximim sentence he could get is 40 years, but the odds are that he won't get the maximum; my guess would be 20 years, to allow his kids to reach adulthood before he is released.
Another interesting question at this point is if we will see the Arkansas DCFS now open an investigation to determine if his own children have been victimized.
Something else I wonder: Jim-Bob is a pretty venal kind of guy, and is widely known to have a really explosive temper. I wonder if there is any possibility that he might encourage Anna to leave NW Arkansas, in order to essentially remove Josh and his nuclear family from the Duggar narrative. Her parents live on a large plot of land in rural Florida, but do not have much money; one scenario could be that she could be encouraged to move back there and given enough money to build a home on their land, where they could help her raise the children. (If her parents have any sense at all, they will insist that JB provide her with ongoing child-support payments; it's not like Josh is going to be sending them any money.)