You can use the -d option in PVRTexToolCL to do this automatically. If you want it during compression it’s fairly straightforward – just add “-d” and an optional filename to output it.
If you want to just do it with any list of already compressed pvrs, unfortunately you’ll technically still need to compress it first. However by setting the decompression to “r8g8b8a8” you’ll sidestep any additional work. I’d suggest using the following command line to do so: