many congratulations for your VCP6-DCV
Next step would be based on your job role, and area of interest, based on that you pursue either DCA or DCD track of VCAP6.
and if you do both, that will earn you VCIX6-DCA.
regarding next course, vSphere Desing and Deploye FT for v6 course is a nice course but I would recommend going through course content first and see if that's what you want.
other courses like vSphere 6, Optimise and Scale and/or vSphere 6- Troubleshooting Workshop might also be very help full in administration, performance tuning and troubleshooting aspects.
but again go through course content to see if the course is meeting your expectations.
I agree with Narendra's reply.
I do just need to make one small correction, if you achieve both VCAP6-DCV Deploy and VCAP6-DCV Design you would gain VCIX6-DCV. (there's no such thing as VCIX6-DCA)
I'd also propose that you consider stepping out of the DCV track into something other than vSphere, if there's value in that for you and what you want to do - you have training and certifications for NSX, vRealize Suite, and Horizon and Airwatch.