Printer driver Canon Pixma ip5000 for Catalina

How do I know except when it works after the upgrade (or not)?

That's what you'll have to do. However, you can download and run GO64 to see which of your apps are 32 bit and will not work with Catalina. It also shows those apps that may be 64 bit except of many one component. See if the Canon utilities are 32 or 64. That will give you a hint on the drivers.

If the printer won't work with Catalina give this free, open source drive a try: Gutenprint.

Canon does not provide drivers, or supplemental software for Mojave (10.14), or Catalina (10.15) for the PIXMA IP5000 device. It is not supported by Apple's AirPrint solution either. The fact that this device continues to work for you on Mojave likely has to do with 32-bit driver support from an earlier Canon driver release.

You may or may not be able to use Apple's Image Capture with it on Catalina, but there will be absolutely no Canon support for it there.

As you can see, I used the printer driver yesterday!! On Catalina 10.15.3? You already said it works great on Mojave, even though Canon does not show it supported there.

Even though it is shown as 64-bit software, according to Go64, that does not guarantee that even though it is 64-bit software, that it is designed to work with Catalina. If it does, then you would have lucked out, but as I mentioned earlier, Canon does not provide any application, or driver support for the IP5000 from their website for High Sierra (10.13) or later. Support for the IP5000 was not included in the last Canon Printer Update v3.4 from Apple in July 2017 either.

I agree with Old Toad that you simply won't know if it will work until you upgrade to Catalina 10.15.3.

Although Gutenprint has experimental support for the PIXMA IP5000, there is a bigger issue in that for several months now, GutenPrint ˙has the following caveat about installing on Catalina, and the principal reason I did not mention Gutenprint earlier.

I don't use Gutenprint. It will likely work fine on your Mojave installation provided the installation steps are followed, and with a bit of luck. You would likely need to reinstall it for Catalina, and the caveats of Gutenprint on Catalina have already been shared.

Ensure that you have one last completed, Time Machine backup before starting the Catalina upgrade. By doing so, you have a means to return to Mojave just as it was before the upgrade. This is key.

I forgot that the IP5000 is a photo printer, so forget about Image Capture which is used for scanning.