Should I go for Magento Developer Certification now or should I wait for the Magento2 certification?
If you feel confident on getting you Magento Certification for 1x, I'd recommend go for you certification. I work with a lot of Enterprise level ERP systems using Magento(50-1000 employees) and there is no plan in the near future to move to Magento 2 as there isn't an absolutely upside at this point for the financial cost. Plus there really isn't anything 'out of the box' that works with the major retailers for small size companies. Truthfully I'm not sure why anyone is moving to Magento 2 right now. It just cost more and there is a lot less support on the market.
Magento 2 will be better supported by the community and other mid/large size companies at some point, but it'll take some time. There will plenty of work for you certification for sometime.
However, always keep in mind what YOU want to do with you certification. Many small time companies will take the leap to Magento 2 early and it's easy to work with smaller clients than larger ERPs.