Kanye is definitely on the downswing. However Kanye actually has a lot more musical talent than most of the dudes in the mainstream, so you cant really count him out. I think the main thing is he really isnt too focused on music anymore, and he has a lot of influences around him that are probably good for him as a person, but not as a musician.
If Kanye had a serious wish to express himself musically, and stopped taking advice from those who see him as an 'auteur' or who are trying to just 'capitalize'... then he has the musical talent where he could make a new good album. Similar to how even decades after he lost all relevance John Cash was able to put out a song that really resonated with people right before he died... Now is it likely that Kanye is going to stop focusing on fashion, and film, concentrate on music, put aside the 'distractions' and release some good music AND also recapture mainstream acceptance... unlikely... i mean James Brown, Michael Jackson, Stevie Wonder all lost relevance... but they still put out some good music after their time at the pinnacle was over.