Yeah, it'll give you future updates free of charge. Most of itch.io is like that. Typically, you'll have downloads for a game locked behind specific prices. Whenever you "buy" a game, you'll have a dollar amount attached to that page and whenever the dev uploads a new version set for the new price or lower, you'll get access to that content.
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Thank you for the information Lotus Eater Machine. I thought that was how it worked but I ran into a couple of games recently that the forum postings had several complaints of buying and then having to buy again for updates for a particular game. It envolved more than one game so I always ask to be sure. Have a great summer!