Very unlikely to get a Traverse. I did not see any at all in 2 weeks at LAX or PHX. Hertz did not buy that many GM cars during 2016, and the Traverse was not one of the models they acquired (and no Enclaves, either).

If you booked an L4, you are most likely to get a Pathfinder. they've got more of those than everything else put together. There are still quite a few Dodge Journey 7 seaters out there. Some Explorers, too. I would say it is quite likely you will be upgraded to a T or T6 (there are a lot of Yukons on fleet at present).