Yes it's an interesting trend. I integrate with a good handful of systems in my current work and the most important ones we integrate with are SOAP based. The concepts behind a WSDL are great in theory, but they end up incorrect or unmaintained in practice (at least with the systems I integrate with). There's something freeing and flexible about a plain REST API that makes developing your own wrapper nice and simple, but if all communication is between internal systems, a contract based approach seems great.