I'm using LR 5 but have been using LR since Adobe released LR2. I have LR2 and LR4 on my mac that I'd like to trash as I'm trying to clean up my HD. If I do this and need to access old RAW's that were edited using LR2 or LR4 catalogues will LR suggest I upgrade the catalogue? I don't want to be locked out of being able to access those images if I ever needed to. I've had similar problems with this before and I'm nervous about trashing. I keep separate LR catalogues for each event I photograph. These are all on portable HD's. Thanks.
If you open an older catalog, Lightroom will upgrade it. To be more precise, it'll upgrade a copy of the catalog, so you still have the original. All the processing from previous versions of Lightroom are available in the current version. The decision to remove the apps is entirely up to you.
Thanks Sean, that's helpfully explained.