With Denise Savoie's retirement, Canadians will see at least three by-elections in the next year or so - one in Durham, one in Calgary Centre, and one in Victoria. We may also see one in Etobicoke Centre, but that depends on the courts.
The date for these by-elections, at least the confirmed three, will likely be before January 2013; this is because Calgary Centre, which was vacated by Lee Richardson in June, must be called by Harper before January 14th. Given Harper's propensity to call clusters of by-elections in the past, its likely we'll see writs dropped in November or December.
And even with Victoria's addition, they're going to be very boring (except for Etobicoke Centre, but again, focusing on the confirmed three).
Its safe to say that it is very likely the NDP will retain the riding in a by-election, barring exceptional circumstances, or exceptional candidates from either the Conservatives, Liberals, or the Greens, who deserve an honourable mention in this post, given their strong results and the fact that its next door to Elizabeth May.
That doesn't mean the Conservatives can't win, though, and they have in the past with Allan McKinnon, though after his retirement, they've not played any major role, sitting around 20-30% since 1988. They did come in second in 2011, but with only 24% of the vote. Patrick Hunt, their 2011 candidate (and also the '93 Reform candidate) may or may not run again.
The Liberals had a good run from 1993 to 2004, with Anderson keeping the seat red under Chretien and Martin. However we've gone down since then, ending up third in both 2008 and 2011. Even our 2011 candidate, Oak Bay Mayor Christopher Causton, was unable to pull us out of the fire. One wonders if Anderson could be convinced to run again, given that he is still active in politics.
But even if he did, he'd have a tough time of it based off of the 2011 map. The NDP dominated in the most important parts of the City of Victoria proper, while the Conservatives did better in the east-coast suburbs and the Liberals registered a few points higher in Oak Bay. The Greens also did well around Fernwood and the downtown core, though again, this is the Lizzy May effect in full swing.
Provincially the riding is cut into three ridings, Victoria-Beacon Hill, Victoria Swan Lake, and Oak Bay-Gordon Head, held by two NDP and a BC Liberal member each, including former BC NDP Leader Carole James. I doubt that either NDP member would be interested in jumping federally when provincially they're poised for a sweeping win, but BC Liberal Ida Chong could be a potential pick for either the federal Liberals or the Conservatives, though how well that would go over, I'm not entirely sure.