In case you decide to remove xscreensaver from future Debian distributions, I have a suggestion:
On whatever substitutes xscreensaver, I would like to suggest that you include the option to turn the screen "blank" in addition to "turn screen off" when the screensaver kicks in. Some screensavers just turn the screen off, and upon restart of the screen, some hardware crashes (sometimes intermittently) and renders the computer unusable. I've seen quite a bit of that. Also, I want to point out that I am very in favor of eliminating this rude & disruptive "warning" ASAP from stable and all other Debian branches. If you release code with a free, open source license, you must understand and be prepared that your code may be modified and used as other users see fit. Cheers, Jamil