That's a really good question. A good question that I cannot answer for definite - if nobody knows, I might email Yonex about this. Here's my take on it: peeling the sticker doesn't affect the racket physically - it won't do any damage. They can easily confirm the authenticity of the racket from its appearance and serial numbers so peeling the sticker shouldn't matter. Plus, racket stickers fall off sometimes - especially when you grip up the cone. I can't see there being an issue. Before you go and do it, wait for someone else to confirm. On a side note, the weight and tension thing is now engraved like the serials so it's unlikely newer racket owners will have this dilemma.
as far as i know, there shall no problem not to have sticker for warranty. just no physical damage to the racket for warranty claim.