I have over 100,000 servers located in routing diverse datacenters with 4byte ASN numbers and have not had 1 problem or complaint related to the ASN for not able to communicate with the datacenter. The first 1 did make me really nervous for all of the reasons already mentioned but turned out to be a non-issue.
While it would be nice to see community string support increase to 4byte, I think this is more of an educational challenge for the IXPs on how to setup your community strings to work and not really a technical problem. Bryan