That would be hilarious, if all these tablet rumours were simply about the same form factor device, but with a higher resolution screen. The more I think about it, the more I doubt it's a tablet. Unless the tablet could fold, or was still close in size to the existing device.
Yep, I think it's very likely just a new iPhone iteration with a higher resolution screen, instead of a tablet. The more I think about it (from a developer standpoint), the more I think scaling the iPhone OS up to a tablet-sized screen (essentially a small laptop screen) is full of tricky issues that need to be worked out with special API/OS enhancements to handle it well. Some of these things the developer can do, but others are really up to Apple to provide solutions for, for example adding support for multi-column table views, split panes, scalable toolbars, etc. Like if you take a scrolling list view on the iPhone (say your Contacts list) and scale that way up, you end up with either a tiny list and a lot of wasted space on the screen, or gigantic text that isn't using the extra pixels efficiently. Yeah, you could use it, but it'd be an awful user experience and very un-Apple-like. I think a tablet interface would require a major modification of the iPhone OS. It sounds easy when you first think about it, but it's not, and desktop OS X is not the answer either (even less so IMO).