"They are here for ages."

Translation: Maen nhw yma ers achau.

[Nate_J]

This sentence really means something more like "They have been here for ages," right? So how would you say "They'll be here for ages?" I don't think ers would work, but I don't know what else to use

[ibisc]

You are right - ers here is looking back in time (and the English translation has now been changed to reflect that.)

Looking forward in time you could use am:

• Byddan nhw yma am oesoedd

[Nate_J]

Diolch!