I also disagree with the plan to package gimp3 and leave gimp at 2.x. Users expect to install gimp and get the latest version, and version 3 won’t be “new and different” for long. This is how compatibility packages work almost everywhere else in the distribution. It makes eventually retiring the old version less disruptive, it makes the latest version the implicit default (Fedora is “First”), and consistency with the usual practice in the distribution reduces user confusion.
How would we feel if we had to install gimp2 today because someone decided back in 2004 that gimp should stay at 1.x?