Perhaps the way to push security into the industry is to use consumer's rights to their full capacity. In the EU if you buy something, you get 6 months of warranty and 24 months of implied warranty.

If you buy an Android phone and stop getting updates after 18 months and there is a new security hole, you should return the phone to your dealer and demand your money back. After all, it's relatively easy to prove that the defect (the security hole) was already present when you bought the phone. The dealer must fix the defect. If he can't, he must take back the article. He will then complain to the manufacturer. The pressure from these complaints hopefully lead to a change of behaviour by the manufacturers (i.e. provide two years of security updates, for example, even if you buy a new phone that's already been available for a year or two).