I'd honestly like to wait and see how this turns out before I say anything about it. I think that if they do it right and have the shops and school really close to the way they are in the books and don't make them appear to be a cheap, poorly put together tourist attraction it could go far.
For all anyone knows, the Harry Potter fad could stick around for years. I mean, look at Star Wars. I hate those movies with a burning passion, and yet there are STILL several fans out there that love it with all their hearts. Not to mention it's been around for quite a long time. To be competely honest, I thought the 'fad' would die off after the first few books came out. I had never heard of there being so many obsessive fans over a BOOK...until I starting seeing Harry Potter posters go up all over my middle school and heard people talking about it all the time. That was when I started getting curious about it, bought the first one at a book fair, and got hooked.
So! I think that if this 'Island' is made the way it needs to be and the fans of HP stay fans (and I'm talking about the books here, not the movies), it could be extremely successful. Don't judge it this early on, because you never know. But I'm still reserving my true opinion on this until I see the actual attraction, because if they don't do it right it will go down the drain fast.