China Southern and China Eastern are not in very friendly terms. First, China Eastern is expanding in CAN (rapidly), China Southern's home turf. Second, China Eastern bought stakes in AF/KL, of which China Southern's best buddy KL is in. The full effects are unknown yet, but conflict of interests might develop. Third, two airlines will compete head to head in Beijing new airport very soon. Last, currently China Southern and its affiliate Xiamen are both in SkyTeam, there is no room for a fourth Chinese mainland airline, or the fifth from Greater China region in SkyTeam. If Sichuan is to join SkyTeam, I can see China Southern exit as an exchange.

So I think it is crucial to watch Sichuan Airlines. If it joins SkyTeam I think China Southern's days in SkyTeam is numbered. If it joins oneworld, it would not mean China Southern would not join too, but China Southern would be watching Sichuan for years before deciding on jumping the ship to see which one is better suited. That is my personal opinion so may not worth anything to any people. Pure speculation only.