I think Korea is going to be favorites and for the right reason obviously. I don't think they've been sloppy (with the exception of some accidents in champ select maybe), but I'll be honest in saying that I haven't been keeping an extremely close eye on it. Either way, anyone in Korea (except maybe CJ) can take a win off of anyone, so I think they'll come out of it pretty strong.
LPL is a little odd, but it's the LPL so what do you expect? Only RNG and EDG have really shown consistency imo, the third seed for LPL probably won't make it very far, but EDG and RNG can probably put up a fight if they don't choke or something.
EU I haven't seen much of, but G2 and FNC are definite seeds thus far, H2K will probably be the 3rd, but I don't know about how well they'd do at Worlds. Also, bigger surprises have come before. I think it was either last season or 2014 when NA was expected to do decently while EU was considered an underdog and the exact opposite happened when no NA teams made it out of the group stage while I think all of EU's teams made it out, so I wouldn't count EU out yet.
NA is looking decent, but I don't think the top teams are being tested enough. IMT and TSM are looking like 2 of the seeds, but the last seed is just a crap-shoot at this point. Envy looked like they could pop onto the scene and take a spot, but they're sinking like a rock now. Echo Fox is dying in a corner, NRG is trying to keep their heads above water, Apex is tilted to hell, P1 is coming back to life, but might be a little too late. C9 and TL are the only ones who can really be considered able enough to put up a fight at Worlds currently imo (CLG is looking better, but need to get some polish before they're ready imo), but with the Championship points CLG got from Spring, they might still make it.
LMS is an interesting look based on how JT and FW have been doing. AHQ seems to have dropped a notch, but they might make a run during playoffs or their qualifiers. I think they'll have both make it out of the group stage with at least one of them topping their group.
IWCs are interesting to think about. INTZ has already qualified for the IWCQ, and they place 3rd/4th at the IWCI, so maybe they improved a bit to get them into Worlds. I think either Turkey or the LCL will take the 1st seed and probably take a few games off some teams considering Super Massive almost got some games off a few teams at MSI. I don't think they'll get out of the group stage, but it would be interesting to see if they did.