The legacy ESB

3-5 years in the future from now on, many companies who thought that they bought a SOA by buying an ESB will be faced with the issue of buying some new infrastructure, maybe a new ESB, packed with new features. But they won't want to replace their old one, full of cranky old orchestrations who nobody in the corporation does any more how were done and that nobody want to touch because they just work...

Then the company will realize that they will have a legacy ESB. And if they buy something new, it will run just as fine, being integrated in the new infrastructure. Hopefully they will learn, then, that the ESB is not the center of a SOA at all, but just another provider of services, just as so many other things in a SOA.

The typical three-tier SOA (legacy-orchestration-frontend) is not a reference Service-Oriented Architecture; it is just a way of building integration services / applications.