I reckon that although Merle seems aggressive and slightly deranged, on the inside he only wants the best for his little brother, and will fight for what he believes is right in the end. So following that... I think he'll want to join Rick's group, but Rick (for obvious reasons) won't want to let him join. Daryl will try to convince the others that Merle's a useful ally, but Rick won't have a bar of it, so he'll lock Merle up in a cell and keep him there, and possibly torture him/hurt him for what he did to Maggie and Glenn? Not sure, though.