Back in SCS Vegas Pro days, some included plugins worked in future versions, and some didn't. Also, coding changed when Vegas Pro transferred to MAGIX management, so some plugins needed to be updated by their developers to continue functioning in MAGIX releases of Vegas Pro - sometimes at a cost to the customer, sometimes not.
The best way to check out if Nectar Elements V1.0 works in VP16 is to download and install the trial version of VP16 - that will provide you with a definite answer. The good news is that different versions of Vegas Pro can exist on the same computer - the trial version of VP16 won't override VP13.
Of course, as you ask in your post, someone may have actual experience of iZoptope's Nectar Elements 1.0 in VP16 but, just in case, there is another way of finding out.
In my experience most of the legacy SCS Direct X plug-ins work in VP16, The (Direct X) iZotope Mastering suite that came with Sound Forge Pro 9 and 10 does not, It does work in the older 32 bit Vegas 9 and 10. It also works in 32 bit Sound Forge Pro 12, I have not tried them in 32 bit SF Pro 13, I cannot find the authorization code for the iZoptope VST Nectar Elements so I do not know, I suspect it will if registered through iZoptope In addition my Sonitus Ultrafunk Direct X plug-ins do not work in VP16 either but the VST version does.
I got my iZotope Nectar Elements with VP13 .. works for me in VP16. Very hard to say the exact version .. the original install file was: iZotope_Nectar_Elements_v1_00.exe .. Worked in VP14 and VP15 too.
The issue is that the bundled version creates a "bundled" serial number. To use it in newer versions of Vegas, you need a retail serial number. You would need to provide info that you received it as a bundle to Vegas Pro 13 and request a retail serial number in order for it to work in newer versions.