"nec sit terris ultima Thule" - how should terris be interpreted?

Question

Seneca's Medea:

Venient annis saecula seris,
quibus Oceanus vincula rerum
laxet, et ingens pateat tellus,
Tethysque novos detegat orbes
nec sit terris ultima Thule.

I have my doubts with respect to the grammatical function of terris (it results in slightly different meaning; in some of those, for example, Thule is not considered to be part of the terrae):

• ablative of place ("farthest in lands") - but without preposition it makes me wonder.
• ablative of separation ("farthest from lands". i.e. "from/of all the lands, Thule isn't the farthest") - I would usually, maybe wrongly, expect the genitive in those cases.
• ablative of separation ("farthest from lands". i.e. a very remote place distance-wise from the "lands")
• dative ("farthest for/to the lands")

Answer 1

(For reference, these are lines 375–379.)

I'm not sure it's necessary to link terris as closely to ultima as you're doing. I myself construe it as a dative: 'nor Thule be for the known world [the] remotest [spot].' Specifically, I think I'd take it as a dative of possession: 'nor the known world have Thule as [its] most remote [spot].'

Still, a looser English translation would make it sound as though the Latin were using a local ablative: 'nor Thule be the remotest spot on earth.'