My tinnitus almost completely went away after about 1.5 years following a severe acoustic trauma accident. Went from very loud and chaotic with several tones and noises to barely audible unless in a totally quiet environment. I have about 40 dB hearing loss around 4 khz bilaterally from the acoustic trauma.
Then, this summer I, in an extremely stressful situation forgot my earplugs at a party and now I have about 70-80dB tinnitus (subjective mml) for several months. Even though audiogram is basically the same (audiologists seem to think 10dB difference here or there is nothing to worry about), I now have trouble hearing people talking in noisy environments. and my tinnitus is severely limiting my life. Biggest mistake of my life by far.
But yes, tinnitus can improve even though you have a documented hearing loss.