I honestly don't see what's wrong with changing up the movesets. We don't want the same game over and over do we??
Before this new pic-o-the-day, I was actually hoping the beetle was going to be Link's new side special, in one form or another. But, alas, it seems to indicate its an item, not a part of a moveset. If you want to get picky you COULD argue it might still be both, like Samus's screw-attack up-special and the screw-attack item from Brawl. But I doubt it now.
I agree that the boomerang is more iconic, but there are lots of characters with random-as-hell movesets taken from obscure places in their past. Sometimes that's what makes Smash Bros so colorful. But, seeing how dynamic the new characters are, it does sort of cast a shadow over the classic Smash Bros cast. A new move or mechanic would seriously breathe new life into a Smash original like Link. So, I wouldn't say no to a new side-special... but what they should REALLY do is make Link's sword shoot a weak beam when he uses his standard attacks, but only when he has 0% damage, as an homage to the classic Zelda games. That would be a new mechanic that would make Link stand out again.