Translation:here and there
Proper Arabic: hu-ná
As far as I know in Saudi Arabia they say it as "hnayya" - probably western areas there that overlook Egypt across the sea do have the tendency to adapt an Egyptian dialect influence and say (hena) or (hina). In the Levant they say (hón) or (hown), and maybe (hawn) as well. Far west like in Morocco, it's probably more like "Hna"
All in all, the proper Arabic one is Huná.
The fact that there are no words coming afterwards isn't self-evidently a reason to drop the final vowel. I suppose it's related to the fact that Arabic tends to require vowels at the end of a word if the following word begins with a consonant? Arabic version of euphony. French does it differently - it doesn't mind two adjacent consonant, but tends to avoid adjacent vowels.
Well, in Quran for example, when one reaches the end of the verse (marked with a special sign and a number) then typically the end of the word is "stable", meaning the last vowel is not pronounced, as the sentence is complete. If the reader decides to read the last vowel in the verse then he or she MUST continue reading into the next verse.
All in all, in Arabic in general, we don't deem the last vowel necessary if the word is at the end of the sentence because the meaning is complete. Adding it and going silent do sound weird (for us). There are very specific instances where the last vowel is kept (e.g. instances of speaking to a female).