After reading your post, I searched the Internet and found that Alison made the announcement on the Ellen DeGeneres Show. Alison said she will be on the show all this year, but without an exact time yet for when she is leaving. She doesn’t know how they will write her out of the show.
I just hope she comes back to the show at some point–maybe after her children are older. I for one will certainly miss her, but I understand why she is leaving. I don’t know how she juggles all the balls in the air as it is.