First of all you have to picture it like Shawn Did and Ric Flair did (for a brief period), on the last match fo someone who is not changing jobs and is actually retiring it has to be with someone the probably would like to steal the Show with, does not matter to push younger talent in these case (not saying they shouldn't or the couldn't be but it has being shown otherwise), also eventhougn the person who retires the other gets a big rub, but is not like they usually need it, examples of this:
Stone Cold defeated by The Rock at WM 19.
Ric Flair Defeated by Shawn Michaels at WM 24 (and none really though Ric could beat Shawn, for real).
Shawn by Taker at WM 26.
Also I really don't thing it will be either Goldberg nor Sting since they are not with WWE and even if Golberg gets there I really don't thing they will give him the privilege of Taker's last match, sorry but the guy has had a good career but has not urn that right.
For that reason I really don't thing that either Swagger or Morrison will be there either.
I can see the Logic with Kane if Kane wants to be there because of the story the have shared and the respect they have for each other.
Edge, Cena or HHH could be other posibilities since all of them have many years with the company and have been succesful in it, with HHH being the More seasoned guy of the 3, only 3 years before Edge and John wth only 8 years there (I know is a lot but still almost half of HHH tenure with the company) and the venue probalby will be Survivor Series, since it is the PPV in which Taker debuted and like someone else said, keeping the Mania Streak.
For me personally as a Taker fan I would t see either Punk, Kane or Edge as Taker's last opponent, with kane it will go like a transition because of the "brotherhood" storyline but I don't see that much happen.
With Punk or Edge as faces and after really Punk stablish himself as a Main eventer (Punk is on midcard now for some reason, big part of Smackdown but still has to get that believable win over someone not named Jeff Hardy in a hard fought match, hope it happens soon, though) and Edge stablish himself as a Real face with enough support for something like this match.