'Adobe CS5 will ship in April 2010' according to
http://cs5.orgAll i can say about illustrator is its good for working with vector graphics which stay totally crisp no matter what magnification (Logos, posters etc). Its also great for working with type. It has many options in regards to type layout. Knowing how to use the pen tool is important in illustrator.
quote from another website:
If you need to acquire, modify, print or deploy to the web images of a "photographic" nature, then PS would be the program of choice. If you need to create complicated graphics like maps, logos, schematics, or even publications for print like ads, brochures, menus, etc, -- particularly with typography -- then Illustrator is the one.
The above is a basic explanation. Hope it helps.
On a different note, I was having a look PS CS5, and they have made some major changes with regards to photo manipulation side of things. Like you can use the magic wand tool to select a hairy object like an animal and the hairs will stay crisp. Looks pretty amazing.