Offering the tablet with the option of a stylus would be a good move on Apple's part. It opens up the tablet much more.
Think about it, I mean actually think about it. Steve Jobs said he didn't like having to use a stylus when we have a perfectly good "pointing device". Pointing, not writing, not drawing, not painting. So, for basic interaction (web surfing, OS navigation, reading, ect.) a finger is all you need. Why on earth should you NEED a secondary device when a finger should work! Consumers will (and currently do) love the lack of NEED for a secondary device.
But then there is all those niche markets that tablets have belonged to exclusively in the past. The ones people keep citing as the "only people who would buy a tablet". All those people who need a computer that they can take notes on while standing up and moving around. Artists who want a way to sketch out ideas anywhere. If Apple made a tablet that was for consumers only, they would loose all these other potential sales. Why do that when the only thing they would have to do is include an option...and emphasizing this...OPTION...to use a stylus for some applications. A consumer would never need to take the stylus out.
So how Apple store the stylus? Certainly, there would be a need to store the stylus in or on the tablet somehow, right? Easy. My old HP tablet laptop came with a DVD drive. However, HP knew that there wouldn't always be a need for that drive, especially as it adds a lot of weight to the tablet (which needs to be light for extended use while standing). So there was the option to take out the drive and cover up the whole with an enclosed...thing.
So what Apple could do is have the tablet come a place to keep the stylus/pen and the covering for that place when you don't have said pen. Then, seperately, you have the option to purchase a pen and place it into the whole when not in use. The eraser portion would sit flush and to eject, you push it in and it pops out just a little bit.
To reiterate, this is just how they COULD do it and it would make a lot of sense. But they may, at least for the start, just focus on it being a consumer device. But I don't think we should just brush off the idea of Apple doing this period. It would be like brushing off the idea of Apple including the option to pair a bluetooth keyboard with it because it has a software keyboard. I am sure a lot of people would like to have that option for extended text input.
It all depends on how Apple decides to market this device and their long term plans. It may start directed at consumers and open up more in future generations. In any case, this is all so exciting, I may explode in delight!