There is a Midrash ([Shocher Tov][1] [146][2] I think) referenced by Ri ibn Shu'aib (14th cent.) in his drashos to Torah (Matos-Masei) that pig will become permitted in the future. the Or Hachaim to Leviticus (11:7) explains that pig will change biologically acquiring the sign of a kosher animal (chewing cud in a addition to split hooves).

While some commentators understand the laws of kashrus as spiritually purifying (e.g. Abarbanel (commentary to Shmini cited and translated [here][3]), some commentators indeed presume that kashrus laws relate to health (such as those Abarbanel quotes there). They would either dismiss this Midrash (see [here][4]), posit that the biological changes would similarly make it safe to consume (assuming like Or Hachaim that its physical makeup, rather than halachic status will change), or conjecture that although it would remain unhealthy it would be permitted for whatever reason (after all, not every unhealthy food or behavior is forbidden).

Although generally the Torah's laws are immutable as codified by Rambam Hil. Yesodei Hatorah (9:1), this Midrash probably refers to the Messanic era in which even Rambam conceded changes may take place (see Hil. Megillah 2:18). Furthermore, if understood like Or Hachaim that it will change physically perhaps even Rambam would agree that with the sign of kashrus it would be kosher.

Current social changes however certainly wouldn't obviate or negate mitzvos as per the normal rules of mitzvos cited from Rambam.


  [1]: http://en.wikipedia.org/wiki/Midrash_Tehillim
  [2]: http://www.hebrewbooks.org/pdfpager.aspx?req=24744&st=&pgnum=113
  [3]: http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CB4QFjAA&url=http%3A%2F%2Fvbm-torah.org%2Farchive%2Fintparsha%2Fvayikra%2F27-63tazaria.rtf&ei=dbLkVM6XFsSzggShl4T4BA&usg=AFQjCNGRhQTQppQlbKLGJoSApqQdT8W5KQ&sig2=JSavfeG1V_NSA-Ie_tRgiA
  [4]: http://judaism.stackexchange.com/questions/53349/belief-in-medrashim