Ignore is right option because in future if there is need VRops plugin then again need to install.
if you're updating to 6.7 u2 or u3 you should update the Dell OpenManage VIB or you may face Network connectivity /vmotion issues
Yes, the installer will always display such kind of warnings. You have need to upgrade the plugins after VCSA is back in action. VCSA will disable all non working plugins.
this problems is not a VCSA problem at first. The VCSA needs a newer versions (5.1) of OMIVV. As a note .... its now only available in the HTML5 vSphere Client and not in the WebClient any more. The Problem with OMSA only begin if the OP also starts updating the ESXi. Most likely he will so its a very important information.
indeed should have mentioned that it only applies if he is going to update ESXi after.