Guild Wars - Eye of the North FAQs @ Official Site

[Inauro]

The official Guild Wars site has been updated with a series of frequently asked questions about the upcoming expansion, Eye of the North.

<strong class="gold">Do I need to own a copy of one of the previous Guild Wars campaigns in order to play Guild Wars: Eye of the North?[/b]
Yes, because Eye of the North is an expansion rather than a new campaign—and because it is intended for your high-level characters—you need to own at least one of the Guild Wars campaigns—Guild Wars (the original campaign), Guild Wars Factions, or Guild Wars Nightfall—in order to play Guild Wars: Eye of the North. However, you do not need to complete any of the previous campaigns to play GW:EN.

More information.

 

[Cm]

Just a note. Besides the new expansions you can also buy extra character slots so you can have more then the four builds that are allowed with the original purchase.

I found it nice that they have tweaked and added items to the original world as well. Not a lot of major changes but it was nice to see they didn't forget those of us who don't play it enough to buy addon's.