In a talk from Shabbos Parshas Emor 5738 (1978), published in Likkutei Sichos, Vol. XII, pp. 216-220, the Lubavitcher Rebbe bring that most opinions hold that the Jews will be obligate to bring the Pesach Sheni, and points to the Minchas Chinuch (which I didn't look up). emphasis mine:

> The original Pesach Sheni was instituted for those who were unclean or could not otherwise offer the Pesach sacrifice in its proper time. The proper observance of Pesach renders Pesach Sheni unnecessary. What reason, then, is there for a Jew who has celebrated Pesach properly to commemorate Pesach Sheni?

> A Jew constantly yearns for and awaits Moshiach's coming, when the Beis HaMikdosh will be rebuilt. **Should the Beis HaMikdosh be rebuilt in the period between Pesach and Pesach Sheni, the Jewish people will be required to bring the Pesach offering on Pesach Sheni.** [According to most opinions. See Minchas Chinuch, Mitzvah 380.] The expectation of the imminent arrival of Moshiach obligates a Jew, immediately after Pesach, to begin preparations for Pesach Sheni. And, even if Moshiach has not come by Pesach Sheni, it is proper to at least commemorate Pesach Sheni.


  [1]: http://judaism.stackexchange.com/a/7658/603