There's now little detail beyond that, but the Tweet says they're taking "new approach" here, and it "won't be very long between the official reveal and when you can play".
This new Tomb Raider game is definitely Shadow of the Tomb Raider. You can check out the official tweet down below. Square Enix refused to confirm the game's existence back then, but are finally ready to start talking. Based on Square Enix's letter to fans, it seems that the publisher is taking a more Bethesda-like approach, so we can expect the game to come out soon after its reveal.
However, we may have to wait sometime before the game even gets officially unveiled, as the company is waiting for a "major event in 2018" to do so.
Dominic West, Walton Goggins, Daniel Wu, and Kristin Scott Thomas also star in Tomb Raider, which sees Croft living an ordinary life in London until the death of her archaeologist father sets her on a path to becoming the daredevil explorer we know today. Both were critically acclaimed and enormously successful, becoming the franchise's best selling titles, and leaving fans clamoring for a third entry in the series.
With a new Tomb Raider film on the horizon, and the phenomenal reception that the previous two games were met with since the reboot, it's a fantastic time to be Team Lara Croft. The recent Tomb Raider games have been praised for their strong narratives and clever reimaginings of classic Tomb Raider tropes. This is the leaked title of the game and has been rumored for a long time now.