Most probably yes, but it's probably 1-2 years after the release. Itch buyers will also get Steam key when / if the game gets a Steam release :)
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Since itch buyers do get the Steam key as well if it does get a Steam release, if you want to support the game development, it is much better to purchase through itch (if the payment method you use is supported). Steam unfortunately takes a big chunk of the revenue, so on top of tax and other fees, you only get like ~50% of the sale.
Well if you want me to buy off itch im ganna need the games to be more reachable. Not have to download a separate file on my comp everytime. Just quick access. And alot of people are doing this and its getting bothersome. I literally follow several developers and have files of all kinds. I just want a clean library