Wanted: Experienced Delphi programmer to maintain ginormous legacy application and assist in migration to C#

Later on, as the new hire settles into his role... "Oh, that C# migration? Yeah, we'd love to do that. But management is dead-set against it. Good thing you love Pascal, eh?"

I've noticed quite a lot of this where I live (Scotland) and I'm not sure how common this is across IT: a company is using a legacy technology and they know that most developers will avoid them to keep mainstream technology on their resumes. So, they will put out a advertisement saying they are looking to move their product to some hip new tech (C#, Ruby, FORTRAN 99) and require someone who has exposure to both - but the migration is just a carrot on a stick, perpetually hung in front of the hungry developer as he spends each day maintaining the legacy app.

I've experienced this myself, and heard far too many similar stories to the point where it seems like common practice. I've learned over time that every company has legacy problems of some sort, but I fail to see why they can't be honest about it. It should be common sense to any developer that the technology in place is there to support the business and not the other way round. Unless the technology is hurting the business in someway, I hardly see any just cause for reworking the software stack to be made up whatever is currently vogue in the industry.

Would you say that this is commonplace? If so, how can I detect these kinds of leading advertisements beforehand?