I'm currently rewriting much of a Jpeg 2000 for Pascal library. There is a new IO class responsible for decoding and encoding of Jpeg 2000 files instead of only VCL TBitmap descendant. It's cross platform and with only Delphi/FPC RTL dependencies. VCL and LCL TGraphic classes will be built using this IO class but it can be used independently as well (Imaging library will use it too).
New features of Jpeg 2000 for Pascal will be CMYK colorspace support and also indexed/palettized images support (yes, it's possible to have image using palette in Jpeg 2000). These features as well as proper alpha channel definitions are patched into OpenJpeg library. Its team is not very active in incorporating larger patches into their code, so patches will probably always be additional step for people who want to recompile OpenJpeg themselves for use with PasJpeg2000.
You can follow the progress of the new version in SVN repository here: branch v120.