A Tory win is not yet inevitable, nevermind a landslide.
To overturn Labour's majority from the last election, the Tories need a huge swing from Labour to Conservative. A lead of about 12 points in the polls would translate to a win. The latest poll out today after the conferences have Labour advancing to 10 points behind. This probably wouldn't be enough for the Tories to win let alone get a landslide.
As the election campaign gets underway, the gap in the polls tends to narrow.
Cameron seems to have set his stall out for austerity and hard times. But they economy could improve in the next 8 months. The UK, US and Europe are pulling out of recession and good growth is predicted for the next year. If other confidence grows, then the electorate might be reluctant to vote for cuts, job losses and high income tax rises.
http://www.bloomberg.com/apps/news?pid=20601087&sid=aYRYoOMahWcU