Hardly. This is fantastic news in my opinion. I don't see how this could be "ruined" in the first place. The concept of the story is very western. A kid with a book that can kill people. It's very "Twilight Zone"/"Tales from the Crypt"ish. That's what really appealed to me in the first place.
I would love to see what a western scribe can do with the Death Note franchise. Not to mention seeing Ryuuk with Hollywood's CG or creature costume effects, should be a sight to enjoy. In fact, I think I might like it more if they did an entire Creature suit for Ryuuk instead of full blown CG. The more real they can make him the better
But the fact is most people ignore the damn credits and then starts to believe that its original american, i had a dumb class mate who went to The Eye he loves it but he dont know its original an Remake from Hong Kong. and thats my problem, people ingnores the credits. I got even class mates who dont even know that Dragon Ball and Pokemon are from Japan even though the media had said it about a thousand times.
It's not that common, people tend to find out that this stuff is originally Japanese and then just go from there. I myself liked the Death Note movies, more specifically the second one, and as much as I loved Kenichii Matsuyama as L, it would be interesting to see the role as intended, with an English actor. It would be funny if they kept Light and his family Asian and just adjusted the roles for the characters that weren't, or at least didn't "look the part" as people keep saying with Misa and Ray.
I didn't have a problem with the CG used for Ryuuk, but it would be interesting to see him done in a bit of a higher quality.
I generally prefer my protagonists to be somewhat likable, and not insufferable douche bags. Having the bad guy (and that IS what he is) as the main character has been done many times before, and significantly better.