Yes altho there are some special cases where that might not apply, if you buy this for the 5$ price tag you will be able to download all future releases of it with the same price tag
Viewing post in A.I.D.A. - Adult Parody RPG comments
Yes, whenever there is an update at the top of the games page will be a "you own this game" with a download button that will take you to the latest update page to download whenever it updates. Like Stronk said it'll only show updates in the same price category though. Other games might increase the price of the game since they've added more so you'd have to buy it again however, Paccsu doesn't do that at the moment.