The tweet includes an image of the current family of Surface devices: the Surface Pro, Surface Book 2, Surface Studio and Surface Laptop. All of the devices have July 10th listed on the lock screen along with a time of 6:00 PST. That leads us to believe that Microsoft plans to announce the devices at an event tomorrow at around 9AM EST.
As for the previous report which indicated at date of July 13th; it's quite possible that the date is legit. It's just likely that Friday is the day that the device will be available for preorder or direct ordering.
Where will Surface go next? pic.twitter.com/9lz3MJmBAT— Microsoft Surface (@surface) July 9, 2018
It's been rumored that the new device will carry the "Surface Go" moniker when announced; that tip was bandied around by developer Steve Troughton-Smith. Or it could simply be called the "Surface" just like previous entry-level Microsoft tablets.
Whatever the case, the new 10-inch Surface device will be powered by one of three Intel Pentium processors depending on which model you select, and will be available in 4GB/8GB RAM and 64GB/128GB storage configurations. There will be a new Type Cover announced alongside the device and it is expected that it will feature an integrated USB-C port (that means you won't have to use the ultra-expensive Surface USB-C Dongle). It's also reported that the new Surface will feature optional LTE connectivity like its larger Surface Pro sibling (and the budget-minded 9.7-inch Apple iPad).