If you were near a computer at all yesterday, you've likely noticed a number of juicy Eternal Masters spoilers blowing up your social media. What's really interesting about this set, is that the applications for paper Magic and Magic Online will be significantly different. For example, Daze was spoiled as an uncommon in the set, which doesn't mean much for the paper game, though the digital price has tanked from its former 20 ticket price tag. Back in March I advised players to sell off of Daze, and I hope that you all did.
If you head over to Mythic Spoiler, you'll see that we now have six mythics from the set spoiled, with highlights being Jace, the Mind Sculptor, Mana Crypt, and the already known Force of Will. It's important the remember not to focus on the highlight reel when considering purchasing product to open, as ultimately it's the average rare that is going to determine your expected value. Not to mention that Mana Crypts out of Eternal Masters aren't going to be the same as acquiring either existing version with regard to price.
What is most interesting to me at this stage, is that Eternal Masters will be the first foil printing for a number of cards. The printing of Gamble and Toxic Deluge at rare in EMA will hurt the price of non-foil copies, though I expect foils to be highly sought after, and something to look out for as product is opened in your area.
Another interesting consideration with regard to Magic Online is the introduction of cards to the Pauper format. Nimble Mongoose was spoiled at common yesterday, and while I believe that there are too many edicts in the format for this to be significant, there is potentially room to speculate with regard to new decks becoming viable in Pauper. Obviously you wouldn't want to speculate on the cards that are in EMA themselves, though if we pretend that Nimble Mongoose were to spawn a new archetype, you might consider investing in a "rare" common online such as Mental Note (this is not an endorsement of this specific spec).
With several sought after cards announced yesterday, prices for sealed EMA product saw a significant spike, though you have to know that there will be some Etched Monstrosity-type cards on the way. Unless you can get product at or near MSRP, just hold off. It's wiser to consider the singles from the set and how to act according to the spoiler.