VMware certifications are no longer titled after product versions, so if you completed the requirements for your certification this year you already hold the latest certification VCP-NV 2020.

Until the NSX-T 2.4 exam is retired, VCP-NV 2020 can be achieved by passing either the 2.4 exam or the 3.0 exam:

VMware Certified Professional - Network Virtualization 2020 (VCP-NV 2020)​

There's nothing to stop you taking the 3.0 exam now, but passing it won't award you a new certification if you're already a VCP-NV 2020.

There won't be a 2.4-3.0 upgrade exam, for the reasons above.

You'll see on the VCAP pages that it's the VCP year which counts nowadays too - so if you're VCP-NV 2019 or VCP-NV 2020 you meet that requirement for VCAPs.

VMware Certified Advanced Professional — Network Virtualization Deployment 2020 

VMware Certified Advanced Professional — Network Virtualization Design 2020