On Monday, April 12th, Adobe’s having a huge event to announce the forthcoming release of Creative Suite 5.

For users of CS2 through CS4, it’s a great opportunity to see what they’ll have the option of upgrading to.

For users of the original Creative Suite programs—whether you call them CS or version 8.0—it’s a ticking doomsday clock.

Adobe’s long-standing “3 versions back” policy became official upgrade policy last year. Under this policy, upgrade pricing is available only to owners of the previous three versions of an Adobe software title. Users outside of the 3 version window must purchase their next “upgrade” at full price.

So if you’re still using Photoshop CS, consider this the fire under your butt: If you don’t buy a CS4 upgrade before they disappear, your next version of Photoshop is going to be $699. April 11th is the last day you’re absolutely certain to find CS4 upgrades (nobody knows yet when CS5’s actually launching), so it’s a great time to break out any user group or association discounts you may have for the Adobe Store.