Existing V2 camera and buying new V3 camera

Will the wireless camera V3 stack with V2 cameras that are a few years old.

Two things, the V3 isn’t wireless. It requires a power adapter. Second, what do you mean by “stack”?

If you mean stack one on top of the other, yes. When the V3 first came out I had several locations that had both a V2 and a V3 either side by side or stacked on top of each other - so I could compare the performance. There is nothing magnetic on the top side of the cameras, so the top camera just sits on top of the lower camera. Although you could use the included steel disk and adhesive if you wanted it more permanent - I did not.