It's tacky to point out, but if NS's mother were to pass on and NS still does not return afterwards, some would say it's "proof" that she only used her mother's illness as an excuse to quit the series. I disagree. She would also want/need time to mourn after her mother passes away. The death of a parent can make people do major re-assessments of their own lives, so a decision for or against going back to a job might seem insignificant. I've said repeatedly that I hope she will return to the show, but I would totally understand if she didn't. I'm not sure she ever made any sort of promise that she would, either. I guess the deciding factors would be 1) does she need the money? 2) Did she enjoy the role/work? and 3) Is she the type of person who needs work to 'get her mind off things'? There might also be a "4": "Do the producers want her back?" but they've all done a good job of keeping their personal feelings out of the press, so that's all speculation. The length of time they've spent in the "recast process" can be read many ways.