An update on this, as we have some good news to share: OpenResty 1.15.5.1rc0 was released yesterday (see https://github.com/openresty/openresty/issues/353#issuecomment-434153093), so a 1.15 based Kong version is now in sight on the horizon.
We will make efforts to bump our OpenResty code and test subsequent OpenResty release candidates after our Kong 1.0 release (on which we are still working on).
If you feel like hacking around with Kong and gRPC, you can run Kong with this new OpenResty rc already, just make sure to update the following file so that Kong accepts the new OpenResty version:
And of course, tweak the nginx configuration file with some of the new ngx_http_grpc_module directives. If anybody is conducting any experiments on this, we would be curious to hear what you are up to!