Yes but means testing is only one option usually proposed by left wing economists and advocates. They can also remove the triple lock allowing state pension to fall by inflation. How do you means test a benefit that people have paid into all their lives ,it would undermine the whole social security system , people would simply refuse to pay prsi etc , it would be like the water rates protests of a decade ago on steroids.
Also many UK pensioners move abroad after retirement, how do you means test someone no longer living in UK. Its practically not workable anyway