Barely a couple of months old, and already geeks are doing the geek thing and dissecting their 4th gen iPods. With rumours of hidden features flying through the blogosphere, I imagine the dissections will take on a more scientific nature than the usual aimless poking and prodding.
While I wouldn’t put it past Apple to run some marketing gimmick like having a colour screen or bluetooth that are only enabled by a firmware upgrade, I doubt we’re talking about something so earth-shattering. Accessory or Mac-based features are where my money is at – e.g. an inline headphone remote with LCD: this would require a tiny change over the gen3 (ability to send as well as receive commands from the remote), and I could imagine this being included in the gen4, but the remotes not yet being available.