"It's been way too long" possible references
iPhone: obviously not
iPad: seriously doubt it, unless referring to it's lack of touchID
iMac: just had a redesign 2 years ago. Retina reference? seriously doubt it
Mac mini: while very outdated, do you really think the mac mini is an important enough device to be the focal point of an event?... case and point
iPods: No these aren't important to Apple
Macbook air: doesn't really make sense, because no one really thinks the mba is outdated.. so unless its a something revolutionary, which brings me to...
iPad pro/iOSbook Air: this kind of a hybrid device would make sense from the tagline, but I don't really see Apple releaseing this product
Apple TV: I think this is the most logical. Haven't had a h/w update in years. Better hardware is needed for homekit integration. Been wanting an app store for a long time. There is basically a lot of directions Apple could take this device in.