Studios have already tried fooling people by releasing upscaled versions of shows and movies on blu-ray without going through a mastering process. Critics are quick to catch this and people are now more weary about what they purchase on blu-ray. You can now buy a lot of blu-ray content for under $10 that looks no better than a regular DVD played through a DVD player that upscales to HD.
I'm not sure how much is to be made on re-releasing something on blu-ray. I just bought the Star Trek TOS movie set for less than half of retail on Amazon. A few other movies I've bought recently come with 4 discs. Blu-ray movie, regular movie, computer digital release, and extra content DVD. All for under $20. It's getting competitive out there.