Guild Wars 2

They say this on the FAQ ( https://help.guildwars2.com/entries/91220997?_ga=1.78069648.58123725.1379413748 ) : (read the part in bold)

If I didn’t get into this beta, can I still get in to later ones?

Yes! We’ll be expanding the size of the pool of beta testers for future tests. We selected a small number of testers for the first round from our newsletter subscribers. Our next test will use this method as well as the “Portal to the Heart of Maguuma,” an in-game item which has a chance to drop from enemies in Dry Top and the Silverwastes. Players who find this item and are signed up for our mailing list are guaranteed a spot in the next closed beta test!. So, if you want a chance to be in the next group of testers, you can sign up for the newsletter here. Make sure you sign up using the same e-mail address that you use for your game account.

So, apparently you need to drop a portal AND be a subscriber to their newsletter to have a guaranteed access to the next beta. If you have not done so yet, I strongly suggest you do it now if you got a portal.

I was a subscriber long before getting a portal, though I subscribed again after getting a portal for double measure.

https://forum-en.gw2archive.eu/forum/game/hot/About-the-Portal-to-Maguuma-s-Heart/first#post5040126

newsletter will only give out details about the schedule and how to participate, it isn’t required.