The Altaic suggestion has been out of fashion since the 90ies. Of course there are still linguists who propose it, but it is certainly not established. Its status is similar to the Elamo-Dravidian or Haida-Na Dene stipulations or the Meroitic association with Afro-Asiatic.
The reason for treating Korean as belonging to the Koreanic language family is mainly the Jeju dialect, often regarded as a separate language, as well as the historical languages of the three kingdoms of Korea. These languages are now often grouped under Koreanic http://en.wikipedia.org/wiki/Koreanic_languages
(and still separate from Japonic, Turkic and other component branches of the suggested Altaic hypothesis).
As to Rhaetic:
1) It is hardly documented (similar to Harappan and contrary to all language isolates suggested).
2) It is most probably related to Etruscan - http://en.wikipedia.org/wiki/Tyrrhenian_languages
but still as there is so little evidence from that language it is most accurately defined as unclassifiable.
3) Rhaetian has nothing to do with the Rhaetian railway whereas Pataxo for example is spoken within the boundaries of the inscribed area by tribes acknowledged by the nomination file.