Argentina still has to qualify despite being the defending champions? Anyway from your list, only Brazil and Argentina looks certain to me. Competition is extremely strong in CONMEBOL qualifiers. Upsets can always happen and last time it was Uruguay and Ecuador who managed to qualify apart from the two top teams. Colombia lost out and later tried their best to get Ecuador disqualified. Chile and Paraguay lost out as well, and they were also not too happy about it. Peru had a golden chance of qualifying, but they lost to Australia in the playoffs.
The winner of France 1998, which was France, was actually the last team to qualify automatically as the champion. So, in Korea-Japan 2002 we saw this happening for the last time, more than 20 years ago.
Host is still a big issue, of course host will play because it would be hard not to, but when the hosts are growing in size it's becoming an issue. Look at Canada/USA/Mexico right now, that's three teams automatically there, which prevents another 3 team to participate in it as well. I can't really say that it's going to be different or anything but after all we are talking about a situation where too many hosts would mean terrible for other teams.