Though there was some conflicting information back in August as to whether the series would end in February 2009 or May 2009 but it has since been confirmed that the show will end in February. The season is only to have 19 episodes versus the normal season total of 22. Except for Thanksgiving, Christmas, and possibly New Year's I'm thinking we are going to have all new episodes airing from now on up until the season/series finale in February.
As for when Ray's second appearance will be, my guess is it will be either in episode 15.7 or 15.8. I don't see Neela having to be physically present in the series finale. I think it would be cool that Morris would say he got an email from Neela saying that Ray and her found a house and that she will be starting her new job soon.
Of course this is all pure speculation and as hard as it will be; we'll just have to wait and see how it all plays out.