The issue here in Canada has nothing to do with the actual changes to succession - the content of the laws in question is essentially irrelevant to the constitutional problem. We don't even have explicitly documented succession laws at the moment, which is the only reason the government thinks it can get away with this. (By Constitution and common law, we follow the UK policy as it stood in 1982 unless we change that.) The problem is that the Constitution explicitly divorced Canadian law form UK law as of 1982, so a law that boils down to "We will follow the UK's changes to a UK law that we happen to share" is in violation.
Given this context, I would certainly hope that an amendment to allow this - unless very strictly limited to succession law - would not pass routinely. I think the legal challenge is pretty important here, because "We can just ignore major sections of the Constitution we don't like!" is not a precedent I want the Harper government to have. The relative innocuousness of the current issue is beside the point.
EDIT: I don't want to interrupt the ongoing conversation, but... after reading the text in dispute, it's muddier than I thought. The Constitution Act (1982) repeals section 4 of the Statute of Westminster... which is the bit of the constitution saying that UK laws don't apply here, except by consent. Common-law precedent seems to hold that the intent was to strike the "except by consent" part, but... that's not what it says, so there's just enough wiggle room if you ignore precedent. Which, on reflection, might be the goal here... killing the common law is a massive change with unpredictable repercussions, but is liable to leave more power in the hands of the government.