It's likely that at least for the Sega Genesis games Sega will throw out a new collection. The current one is pretty old and has issues, especially with latency.
> THIS SOFTWARE IS LICENSED, NOT SOLD.
> 3. NO RIGHT TO OWNERSHIP YOU ACKNOWLEDGE AND AGREE THAT YOU SHALL HAVE NO OWNERSHIP
If you look at the Steam store page there are numerous reviews from people who bought the collection only to have Sega remove some of the ROMs from the collection making it impossible to play these games that you paid for.
[0] https://store.steampowered.com/app/34270/SEGA_Mega_Drive_and...
The reviews here are complaining about Sega delisting the collection. People that already have it will still be able to play them and redownload them off Steam. They have already delisted some of them (e.g., Sonic 3) and they're still available to those that got them before they were removed.
Well, maybe. Sega might claim that they have only licensed them and you don't own them; a court might disagree, given the big "buy" button and the consideration paid for them.
I'd really like to believe that is the case, but I think we've already seen that is generally not true based on other digital marketplaces (e.g. Kindle books, iTunes media, etc.)
But specifically regarding Steam... this was just last month[0][1]
> Valve is now explicitly disclosing that you don’t own the games you buy from its Steam online store. The company has added a note on the payment checkout screen stating that “a purchase of a digital product grants a license for the product on Steam,” as reported earlier by Engadget.
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> ...
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> Why? Probably, a new law. California has a law going into effect next year that’ll require digital storefronts like Valve’s Steam platform to clearly say that you’re only purchasing a license for your digital media because some companies like Ubisoft and PlayStation were removing digital purchases from users’ libraries, keeping them from playing games like The Crew or watching their old Discovery shows.
[0] https://www.theverge.com/2024/10/11/24267864/steam-buy-purch...