Based on form, Ireland are the team to beat, sure. They didn't impress me that much against SA though. Lineout was absolute rubbish and they controlled the game for big periods but the Boks could have easily won that game if they kicked their goals or that last maul decision went their way.
Also, ask any All Black fan over age 30 what form means in a World Cup knockout game against spirited opposition and they'll tell you: "diddly squat." The best team doesn't always win the tournament and right now France aren't the best team but they're definitely good enough and of course home advantage could be the difference. Mentally they also seem the best prepared of the favourites: not too high, not too low in their expectations and emotions (and for a team that's often seen as being erratic and having a "latin" temperament, that's a surprise).
Tactically, SA will always stand a chance while Rassie is the de facto head coach (poor Nienabar, he must feel like a muppet sometimes). I just doubt whether they have the desire and ability to rise to the occasion again after the heroics in 2019. Also, that year their path to the trophy was easier than it potentially will be this time.
An Argentine team with their backs against the wall can be dangerous too. This tournaments needs an upset because apart from a few games, the quality and drama has been much lower than previous editions.