The level of items from the slots are based on your game progression. You need to finish the game on true vault hunter difficulty to get level 50 items from the slots.
Correct, I'm no on my second play thru at level 40 and still do not see any Level 50 ORANGE items.
I will continue to test this out as I get closer to finishing my second play thru to see how these items progress in level, I have gotten some LEVEL 38 items however, but many are not as good as the purple/lavender items from the gold chest I currently have.
Some of the names however are fun to read