Hi Deepak,
The answer is No.
You can't retrieve the content of Dashboard through RESTful Web services SDKs. As of now REST SDK doesn't have this functionality. The RESTful Web Services SDKs can perform modifications on Webi report, as REST SDK is introduced wih the functional parity of Report Engine SDKs.
You can only retrieve some basic information about Dashboard using Platform RESTful Web Services SDKs, like its name, ID, CUID, type, description, Open Document link to Dashboard last updated date etc.
Thanks,
Shailendra