Translation:See you later!
I wasn't aware of it until now, but when I say it I swallow the ת, too, and I dare say all Hebrew speakers do - if I try to pronounce it it sounds unnatural to me. This is probably the case with all words ending in ת or ט with no vowel. However, this is only if the there's a speech pause after it. If it's followed by any word, the t is sound is pronounced distinctnly.
You right! He doesn't pronounce the t at the end. This link has two Israeli speakers who say it more clearly.
Here I found where we can hear other people pronouncing this: https://forvo.com/search/%d7%9c%d7%94%d7%aa%d7%a8%d7%90%d7%95%d7%aa/
Does the "הת" at the beginning means it belongs to the hitpa'el binyan? Is it the reflexive one (see each other?) ? I am by no means as advanced in hebrew grammar but I dug into it a bit because the whole binyanim thing is super interesting, and thought it seems like this pattern.
So, to answer your question, it is not a composite word, it has only one root. Hebrew doesn't seem to have many composite words that are written as one word.
When one says "see you soon" in English it's not necessarily any different to saying 'see you later'. ie if you say "see you soon" it could be that you expect to see the person later that day, the following day, the following week. Saying "See you later" is most likely to be more immediate than saying "see you soon"