We haven't been saying go out and buy a PS2. Regarding BC add ons, the Intellivison 2600 adapter was released in 1983 as well right before/during the video game crash, only available on Intellivision II, and combined sales of Intellivisions had only reached 3 million anyways. Regarding Collecovision, can you provide any details on total sales and total sales for the expansion module #1? Collecovision was another console that died during the crash of 83 from what I've read. Any info on how much the Power Base Converter sold? I see it wasn't available on the redesigned Genesis 2 except in Europe. I wouldn't expect it to have sold too well considering the Master System not having many great games.
I think a better example than these examples from mostly bad selling systems, affected by the crash of 83, that happened 20-30 years ago would be the Super Game Boy and the Gameboy Player for GC. These sold fairly well, and I think an add on that allowed PS4 to play all PS1-3 games would do even better.