Well that decision would be completely up to that brand/company wether they replace the cocoa butter with Vegetable oil. YOu could very well go to buy some Bakers one day and find that it is ALL hydrogenated vegetable oil...same with Callebaut or Lindt(Lindt already isn't very top notch anyway so I would suspect they "might" use this to their advantage...
Well, if brand X switches to vegetable oil, then I'll just switch to brand Y. Even if a company like, say, Lindt, makes the switch, so what? Then you just use El Ray or Scharffen Berger or Valhrona...
Any high-end brand dumb enough to pull a stunt like this will simply go out of business.
As for brands like Bakers, who cares what thet put in their chocolate? Nothing could possibly make it any worse than it is.