The Tory Party are harder to wipe out than cockroaches, they're not going to fall to third-party status. Also, whilst their current strength with the elderly does owe a lot to high house prices and protecting spending on pensioners, that property is going to get inherited by somebody, and they're then going to be protected by Tory policies. And we're still a country where a majority of people are homeowners, and where those who aren't are disproportionately concentrated in urban constituencies.
So whilst their current electoral coalition may cause them difficulties in future, it's not an untenable one long-term.
Which, again, should be a greater focus for the left than it currently is when it comes to achieving equality etc.
The Tories could eventually be replaced, but it won't be by anything other than another centre-right force. A more right-wing version of the Lib Dems (as suggested above) would hardly be different to the Cameron-era Tories would it? And we all recall how much lefties loved the Coalition and its delightful austerity...
