[PatrioticAmerican]

I thought that a patent requires a person to have control of their invention, and that the invention is not in the public domain, as is JPEG.

[Willie Green]

"ISO will withdraw the standard: JPEG will be no more,"

So the "standard" will cease to exist.
The file format remains known and will continue to exist in the public domain.

[Publius6961]

That is a good question.
20 years is a long time.

[altair]

JPEG has never been in the public domain. I will repost what is written in the libjpeg software:

This software is copyright (C) 1991-1998, Thomas G. Lane. All Rights Reserved except as specified below.
...
It appears that the arithmetic coding option of the JPEG spec is covered by patents owned by IBM, AT&T, and Mitsubishi. Hence arithmetic coding cannot legally be used without obtaining one or more licenses. For this reason, support for arithmetic coding has been removed from the free JPEG software. (Since arithmetic coding provides only a marginal gain over the unpatented Huffman mode, it is unlikely that very many implementations will support it.) So far as we are aware, there are no patent restrictions on the remaining code.