How accurate is the Sudarsky scale of gas-giant classification today? Do the different classes still exist, and look roughly the same?
The paper Sudarsky et al., 2003, which the wikipedia article is based on, is probably outdated by now in two important aspects.
1.) They used equilibrium chemistry i.e. a local theory of perfect, uniform mixing in the entire atmosphere and infinitely fast chemistry. This has been by now realized to be important to correct (e.g. Cooper&Showman 2006 or Tsai et al. 2017) and leads to different behaviour in the spectrum of a planet.
2.) The line-lists they used were inaccurate for many molecules for hot worlds (see e.g. Tennyson & Yurchenko 2017), particularly in the infrared. This would mainly be leading to different computations of the P-T profile primarily, but that of course impacts the emission spectrum and hence the 'Sudarsky class'.
While those effects are impactful, I am not aware of any paper that systematically tried to redo the classification work from 2003, hence we don't know how impactful they would be overall.