The convention actually came into force on December 18th, 2006. However, from Article 28 Entry Into Force:
4. Notwithstanding the provisions of paragraph 2, where any greater relief from tax would have been afforded by the provisions of the 1978 Convention, any such provision as aforesaid shall continue to have effect for taxation years ending on or before the last day of the calendar year next following that in which the Convention enters into force.
So, the provisions of Article 15 which will make the income taxable in Canada only take effect on Jan. 1, 2008.
As for Canadians leaving Korean, the march has already begun and a good deal more will be leaving when the right opportunity presents itself. Working at Korean for 40% less just isn't worth it.