Yes, you will get the 10 tokens. This is because of the same reason given in the answer to this question.
603.6d Normally, objects that exist immediately after an event are checked to see if the event matched any trigger conditions. Continuous effects that exist at that time are used to determine what the trigger conditions are and what the objects involved in the event look like. However, some triggered abilities must be treated specially. Leaves-the-battlefield abilities, abilities that trigger when a permanent phases out, abilities that trigger when an object that all players can see is put into a hand or library, abilities that trigger specifically when an object becomes unattached, abilities that trigger when a player loses control of an object, and abilities that trigger when a player planeswalks away from a plane will trigger based on their existence, and the appearance of objects, prior to the event rather than afterward. The game has to "look back in time" to determine if these abilities trigger.
Basically, all that says that whenever a creature enters the graveyard from the battlefield, the game checks to see what things looked like the moment before the creatures left the battlefield to determine if there's any triggers that need to happen. The game sees that the way things were at that moment included Teysa, Orzhov Scion being on the battlefield, so its trigger happens.
Also, once the triggered ability is on the stack, it no longer matters if Teysa is still around or not:
112.7a Once activated or triggered, an ability exists on the stack independently of its source. Destruction or removal of the source after that time won't affect the ability.