Depends; if the big warning is: "This is not your usual router!" the user is going to say, "Well, that's good, because I got a new one." Car companies don't get support calls when people buy new cars and their old car keys don't work any more. It comes back to the fact that browsers give misleading messages about security concerns, based on the assumption that your router is either a bank or someone pretending to be a bank. If they had suitable behavior for talking to network hardware, it would be easy to have a big warning that is either really scary or comforting depending on whether you know that you changed out your router. I mean, if someone else has swapped your router for a different one without your knowledge, your computer probably ought to give you a big scary warning; just because the attacker who has hijacked your connection to your router is using a router you might have bought doesn't make it any better.