If you’ve not yet received an invitation, all hope is not lost. Blizzard did announce a number of Stress Tests that they’ll be using in order to “put our servers and technology through their paces in a series of stress tests.” These will “extend the opportunity to even more players. Level caps will also be in place to ensure we’re emphasizing the “stress” in “stress test.”
I consider myself a purist in that I would prefer classic to be released as close as possible to the original. Where that is on the spectrum of patch content will be up to blizz. I'm also not vane enough to believe that any single state of the game is the "Ideal" location we should be aiming for. There is common ground that we can agree on, and I would welcome more than a few changes as long as they are made in the spirit of keeping classic on the vanilla rails.
First things first, it’s worth noting that the World of Warcraft Classic beta is already underway. It kicked off on May 15, and since, players have been busy exploring the original realm just the way it was before the many expansion packs released. If you’re looking to get into the action, however, you’ll need to ensure you’ve opted-in to participating in the beta.
All of this is keeping with the spirit of vanilla, which I think is more important than that a specific number be 11 instead of 12. And it would help to "resize the swing" by making the game harder to the more experienced community, and forcing people to re-discover the game rather than simply looking up whatever they want to know on a spreadsheet somewhere.
Like with addons in the current game, you just need to drop any of these addons into the addons folder — find it under /Interface/AddOns/ in the Classic beta folder, which is in your World of Warcraft folder by default. Then once you log on to the game, you’ll want to make sure that the addons are enabled via the menu option on the character screen.
To actually get access to the beta, which has already started and continue to add more players, you need to sign up via your Blizzard account management page. Under Games & Subscriptions, scroll down to Beta Access and visit the Beta Profile Settings page. Once there, you’ll see a grid of available betas you can opt into. Once you’ve checked WoW Classic, hit Update Preferences and you’re set.