On paper, yes, many IFVs are rated to take up to 30mm these days. But I'm positing that even if you gave me Pumas with AMAP-B panels, and they start taking 30mm hits, I'm still gonna get shredded. Even if they take frontal hits and their optics survive the initial burst (magically), I'm not trusting their frontal armor against 30mm. That's their absolute limit. I'm gonna assume it will fail very quickly. And that's already assuming the initial burst came exactly from the front, and not from a weird angle, in which case I'm kaput from the first round. Lets not forget, IFVs are supposed to Fight Infantry, not other IFVs. (That's supposed to be the job of MBTs, artillery, CAS/gunships etc.) If my IFVs start taking cannon fire, I already completely f***ed up tactically.That would depend on the build of the vehicle. Most Modern IFV have modular armor across the frontal arch that is rated to stop 30mm rounds.
There is a general point to be made here, regarding a confusion in the intended mission for many platforms these days, including IFVs. If their purpose is to fight infantry, why are they continually being up-armored so much? All that's doing is making them less effective at their actual mission, which is to support your infantry, against enemy infantry, which requires very high mobility across terrain that can be very unsuited for heavy armor. I suspect it has a lot to do with the marketing teams of all the defense contractors. They pitch these products to people in procurement departments, who are mostly interested in securing their retirement consultancies at Lockheed etc.