[Update]: Turns out I was correct, the update is now live!
The Overwatch test servers went offline earlier today, but they didn't go down with a bang as you would expect, but rather with a simple "boop" and then nothingness. This could mean absolutely nothing at all, but given that Tuesday is the day Blizzard does all of their patches it is a bit too much of a coincidence to simply ignore. In other words, I have a feeling we're going to be able to play Sombra later today!
So just in case this actually ends up being true, and not just the ramblings of a madman who's clearly looking too much into things, allow me to give you a brief summary of what to expect. Since Sombra is most definitely the highlight of this entire update, it would probably be wise to start with her abilities and tactics. Luckily for me, Blizzard has already managed to cover all of that through a brief preview video! Have a look:
Besides Sombra there are also a couple of other major additions. The Weekly Brawl is being replaced with the Arcade Mode - a collection of various custom games with unique rules and exclusive maps. As of right now the Arcade Mode is the home for 1v1, 3v3, games without hero limits, as well as all of the previously showcased Weekly Brawls (excluding the seasonal ones). So if you're just looking to have a bit of fun without stressing about your rank, the Arcade Mode is the place for you. And best of all, you can get 3 free Loot Boxes each week by simply winning 9 games in the Arcade Mode, so there's even more of an incentive to just relax and unwind!
But if you're more interested in the competitive side of things, worry not as this patch will also bring with it a whole bunch of significant balance changes. First and foremost, all ultimates will take 20% longer to charge, so matches are going to revolve less around pressing Q in the correct sequence, and more about proper team skirmishes. As for the balance changes, I can't give you a link to the official list given that Blizzard has taken it down alongside the PTR, but thankfully I did make a copy! Long story short, expect to see a lot more Soldier 76, Torbjorn, and Widowmaker, while Zarya, Ana, and Mercy (due to the ult nerf) will see a little less play.
It is worth keeping in mind, however, that none of these balance changes are official as of yet. Chances are high that they are, but Blizzard might adjust a couple of numbers between the PTR and the live version, so make sure to check out the official patch notes once they finally get posted. With all of that said, all we have left to do now is wait and see whether I'm correct. If I am you'll get to play Sombra later today and everything is wonderful, but if I'm not I do still have something you can do - collect the new Genji skin which is also releasing today. Have fun with that one!