Currently this isn't planned, so the compatibility with older TC versions isn't broken. There wouldn't be any big benefit, since all the smaller numbers can be represented by the larger ones (except for 64-bit unsigned).
Plugin compatibilty should not be a problem if you increase the interface version and the WDX developer checks it in ContentSetDefaultParams. Thus, newer plugin versions should work with old versions of TC.
TC plugins: Autodesk 3ds Max / Inventor / Revit Preview, FileInDir, ImageMetaData (JPG Comment/EXIF/IPTC/XMP), MATLAB MAT-file Viewer, Mover, SetFolderDate, Solid Edge Preview, Zip2Zero and more
I don't return such small numbers in my plugins so it's not a problem for me. But I would return 8- or 16-bit integers with ft_numeric_32 type if I needed it. All your plugin needs is to pass number to TC, so it doesn't matter it is 8-bit or 32-bit.