It remained unchanged for over 30 years, but there are actually two versions of the GIF file format. The second revision, known as 89a, added a few minor refinements like a frame rate for animations and transparency (but only binary, e.g. fully opaque or fully transparent).

PNG could arguably be seen as GIF 2.0, since it addressed the major shortcomings of the format. But since PNG had no animation capability, it could never fully replace GIF which held on for that one niche use.