Please note that this article reflects my personal opinion. It's one that's shared by many judges in the program, but not all of them.
"Wait for the release notes" has become a common response from judges whenever a player asks a question about cards from an upcomming set. Unfortunately, I believe this response is overused.
The original intent behind the phrase was noble. New cards often have new mechanics, but the rules for them aren't released until around the time of the prerelease. During spoiler season, we don't have the answers to every question, so we ask people to wait for the release notes when we'll get those answers.
Unfortunately, I think some judges have misunderstood the purpose of this phrase, and use it as the catch-all response to any question involving new cards. This is unnecessary and unhelpful. If a card from an upcomming set has both trample and deathtouch and a player wants to know how that works, there is absolutly no reason not to answer them. Trample and deathtouch have both been around for a long time, it's been possible to get them both on the same card for a long time, so the simple fact that they're on a new card should have no bearing on whether you can answer.
The same still applies to more complex mechanics. Maybe a new creature says something like "As long as you have 5 or less life, this creature can't die". Well that's certainly a little weird, and no existing cards say exactly the same thing, but the current rules handle it just fine. Cards like Grafdigger's Cage already make it impossible for cards to enter certain zones, section 614.17 explicitly talks about how "can't" effects work, etc.
Refusing to answer questions does a disservice to the players. Players come to judges to get answers to their questions, and if we refuse to answer their question, they feel like their time has been wasted. Maybe they stop coming to us for questions. Maybe they go to a different judge. Maybe they just google it and hope they get the right answer. This is espetially true during spoiler season, when players are excited at all the new cards and are brewing deck ideas to try out. There will be situations where we truly can't give them an answer, but otherwise, do what you signed up to do and help people learn and enjoy the game.
There are two situations when telling players to wait is appropriate. The first is when a card simply doesn't make sense under the current rules. A sorcery that says "All imaginary creatures get +3i/+3i until end of turn" isn't going to make sense until the battlefield is extended to the complex plane.
The second such situation is when there's a compelling reason to believe that the rules on a certain topic are going to change. An enchantment that says "Creatures with power 4 or greater have flying" works fine under the current rules, but due to how the layers system works, would result in some rather unintuative answers. If a card like that were spoiled, it would be a good sign that WOTC was planning to change how continuous effects worked in the next update.
Please try not to guess. If you're unsure of whether a rule is going to change, it's much better to ask the player to wait than to take your best guess. "Maybe" answers in general are poor practice from figures of authority; it's very easy for people to interpret them the way they want or leave out the "this might change" part when talking to other people and contribute to the spread of misinformation. As judges, we should always strive to only give answers if we're certain they're correct.
Do keep in mind that the current rules and the release notes are not the only resources we have. Several weeks in advance of the release notes, WOTC puts out a mechanics article. It doesn't include any of the technical rules, but it will answer most common questions about new mechanics. The rules manager and other WOTC employees will also answer questions on Twitter, Tumblr, Reddit, and other places. All of these can be used to find answers to questions about new cards rather than telling a player to wait.
When a player asks you a question about new cards, consult the resources at your disposal. If you're not sure of the answer, do what you'd normally do when presented with a question that you can't find an answer for- ask someone else. One good approach that Aaron Henner mentioned to me is to rephrase the question into using current cards when possible. This helps the player understand that this interaction isn't a compltely "new thing", avoids the argument of "well how do you know that, the new rules aren't out yet", and nudges people towards learning the overarching rules rather than memorizing specific card interactions.
Players appreciate the judge community and come to us with their questions. Help maintain that trust by truly being an asset to them whenever possible.