Adobe asks to hurry with the upgrade

If you have Photoshop version 6 or lower, you will not be able to buy Photoshop CS3 at an upgrade price. However, Adobe will provide this opportunity for a limited period.

From Photoshop CS3 Beta FAQ : “Will not offer upgrade pricing for more than three versions back on Photoshop CS3.”

Thus, if you have Photoshop version 6 or lower, you will not be able to buy Photoshop CS3. However, Adobe will provide such an opportunity for a limited period, namely, from the announcement of the product (March 27, 2007) to the start of deliveries. During this period, you can purchase an upgrade version of CS2 and get Photoshop CS3 Standart for free. Unfortunately, this offer does not apply to Photoshop CS3 Extended. Prices for the upgrade version of Extended will be known next week.

The same offer applies to the upgrade version of the Adobe® Creative Suite® software package .
By purchasing the CS2 upgrade after the official announcement of CS3, but before the start of deliveries, you can additionally get CS3 for free. So far, however, it is completely unknown what kind of CS3 package it will be (there are usually a few: Standart / Premium / Production / Bundles)
Source: PhotoshopNews