I was not addressing the financial consideration. Only whether they would stop supporting it. AFAIK, they are still supporting the MX20. And that was acquired with a takeover almost 20 years ago.
So in my opinion, I think the 400 and 500 series navigators will be supported for at least 10 years.
As to whether installing a 430 over a 650 today is smart financial move, that's entirely up to the person writing the check.
A year ago I installed a GTN625 instead of a 400W because it was only about $500 more than the used units I was finding. Had I found a 400w that was $1,500 less than the 625, I would have installed the 400w.