By doing some quick test-bookings, it looks like the Eagle is not running at all south of St Louis on April 6th as the train just shows sold out when using any destination south of STL. Check your email to see if you have received any information from Amtrak. On Amtrak's Advisory page I don't see any information, so it looks like they haven't officially announced it yet. You can try calling Amtrak to see if they realize it's cancelled (I don't think they will, I think it will just say sold out for them too), and try to get on the Chief or maybe EB/CS combo instead.