One Piece's Egghead Arc's main opponents appear to have been established. In order to kill Dr. Vegapunk, a new ally of the Straw Hat Pirates, CP0 is traveling to the future island of Egghead. Not many fans are concerned about this, though.
According to general agreement, CP0 shouldn't be able to contend with the Straw Hat Pirates at their present level of strength. However, some people think that CP0 is being grossly undervalued. In addition to having members that are more powerful than anybody understands, their goal also involves avoiding direct conflict with the Straw Hats. The Straw Hats risk losing in a way for which they are unprepared if they are not careful.
How Powerful Are the Straw Hat Pirates in Comparison to CP0?
Part of what makes fans so unafraid of CP0 is who their top men are. Their ranks include the likes of Rob Lucci and Kaku, two of the strongest warriors to ever come out of CP9; they're now presumably the strongest members of CP0. However, Luffy and his friends beat Lucci, Kaku, and the rest of CP9 years ago in Enies Lobby. If they did it once, they can certainly do it again.
On top of this, the Straw Hat Pirates as a whole have gotten much stronger since their fight with CP9. They've received all sorts of power-ups, upgrades, new weapons, and new allies. This is to say nothing of how they recently defeated an Emperor-level pirate crew. However strong CP0 is, there should be no way for them to reasonably overcome this power gap.
As for whether CP0 is strong in its own right, it's hard to say. Lucci's greatest feats since the last time the Straw Hats faced him have been challenging the likes of Sabo and Sanji; not only were both of those fights off-screen but they were featured in non-canon One Piece movies. Even if these can be taken as signs of how strong he's gotten, it doesn't amount to much.
Besides this, however, the combat capabilities of the rest of CP0 are largely unknown. Kaku is probably second only to Lucci as he was in Enies Lobby, but since Lucci's current power is difficult to gauge, so is his. Stussy doesn't seem like she'd be all that strong, but she probably has a Devil Fruit ability that makes her difficult to deal with. There's also the Bartholomew Kuma Seraph they have with them; the Seraphim have proven to be troublesome even for the Straw Hats, so perhaps there is something to be worried about. Besides these four, there may be others CP0 members coming to the island that the audience doesn't know about yet, like the other former CP9 members. If they're all strong enough to challenge the Straw Hats, then the whole Egghead Arc could easily turn into a rebranded Enies Lobby Arc.
Will Dr. Vegapunk need to be
It's also important to remember that CP0's objective is to assassinate Vegapunk. The doctor also made a request of Luffy to take him off of Egghead in Chapter 1067, "Punk Records;" this is presumably to avoid his grim fate. CP0 will probably shoot to kill the Straw Hats if they get in their way, but their prime target is the doctor. The Straw Hats are capable fighters, but there are no guarantees for Vegapunk.
If it was a straight fight, the Straw Hats would probably win. However, this new escort mission could create a handicap for them. They would have to fight off CP0 while preventing them from killing Vegapunk; this includes his main Stella body, his six Satellites, and his giant brain housed in Punk Records. Not only does this make the fighting more challenging on the Straw Hats' part, but if something happens to Vegapunk, it will essentially be a loss for them.