I'm not sure it's actually published anywhere, it's more to do with the fact that if you go to the actual downloads page where you can download each instrument individually, you can easily see they don't have separate downloads for people who bought V8, V7, V6 or whatever. The instruments are the instruments: doesn't matter what V Collection you bought them in. Naturally if you download an instrument that didn't come with VC7, you'll only get it in demo form (such as the latest CS80V, now upto version 4, or Piano V3), but you can download the latest 'dot' versions of anything you originally purchased with your VC7 licence, as well as the latest Analog Lab.
Unlike the stories which surfaced in 2018-19 about that famous software developer with a five letter name known for making image-editing software, who allegedly revoked the CS6 licences of stubborn customers who had so far refused to upgrade to the company's 'rent-an-app' business model, Arturia never proactively-obsolete your purchases.