This being a brand new IFV, I would expect its armour to be proof against anything up to and including 30mm APDS.
In open combat, anything that can punch through the armour of IFV will likely destroy it outright irrespective of what cal ammo the IFV was carrying. The only widely deployed AT weapon that might get through the armour but not completely destroy the IFV would be your late model RPGs, but those should only be a threat in urban combat.
In an urban combat scenario, the troops should be deployed to support the IFV and other armoured vehicles. The crew of the tank would be at greater risk, but the troops shouldn't be put in that much more risk most of the time. To balance this, the 100mm would allow the IFV to threaten things your 30mm armed IFV can only scratch the paintwork of. In urban combat, a 100mm HE shell would also be significantly more effective and useful than 30mm rounds.
What more, if you have 100mm armed IFVs, you don't really need to send MBTs into urban combat situations where they would be very vulnerable. Slap on some ERA and these IFVs should be able to withstand even late model RPG attacks. If the enemy has modern ATGMs or anything that can defeat ERA and punch through the armour of these IFV, MBTs will die just as easily to those weapons, but MBTs are a great deal more valuable.
