Here's my personal hypothesis on what will happen after Barb dies.
First off, Chris is not ending up in a group home. That little theory has been debunked countless times by many people, so it's not really worth discussing in depth.
My personal view on the whole affair is that Barb's death will be a make or break moment for Chris. This will either free him or utterly crush him and the ball is entirely within Chris's court. Once Chris goes through the initial grieving process, one of two things may happen.
Barb has been mistreating Chris and treating him as part of her hoard for quite some time, and it's only recently with her declining health that Chris is able to live more freely and her grip has loosened. Once Barb dies, Chris will be hurt and very sad, but if he plays his cards right, a life without Barb may be better for him.
With Barb gone, Chris has nothing left to tie him to the hoard. He can leave if he chooses to do so (and evidence suggests that he hates living in the hoard). Marvin has stated countless times that Chris can pay the bills and basic rent with his tugboat and the only reason why he's currently begging for money now is because Barb is taking a large portion of his money to pay off her debtors. With Barb dead, that would no longer be an issue. If Chris can get one of his acquaintances or ass-patters to help him find a cheap low-end trailer or apartment near Charlottesville, he could easily survive. He'd be living tugboat to tugboat and barely scraping by, but compared to the hoard, that's a massive step up in quality. There's no way his acquaintances would let him live with them, but in the event of something major like Barb dying, they may help find a place of his own in the middle of nowhere or in a shitty apartment on the lower end of the Charlottesville area.
Again, this is the best case scenario. Worst case scenario, Chris ends up homeless like ADF and is utterly shattered by Barb's death. It could really go either way at this point. However, he's not ending up in a group home.
Just my two cents on the whole issue.