I think I'll put these here:
http://www.gameinformer.com/b/featu...itter.com&utm_campaign=buffer&PostPageIndex=1
http://nintendoeverything.com/aonuma-talks-majoras-mask-majora-and-termina-name-origins-lots-more/
Here, Aonuma states that Termina is actually supposed to be a place that is nearby Hyrule. It just feels like another dimension cause it has connections to different worlds. That, and mostly because the Termina we see in MM does actually exist in alternate reality, most likely, a future parallel to WW's timeframe and TP's timeframe. But that doesn't mean it's Hyrule, cause it's not. Aonuma confirmed so.
Here, Aonuma further confirms that Termina is just a nearby country/kingdom/nation nearby Hyrule where people come and go. Heck, we even see Link the goron in MM. It's unknown whether he's the same Link the goron from OoT or a descendant of his. And the fact that he clearly seen coming from the east and not the North further confirms this. That said, that also confirms where Termina is, that it's west of Hyrule (where Link the goron is obviously coming from in MM).
I'll explain more later. Right now, I'm tired.
I thought we were talking about the tetraforce though and how it might exhist in Termina - not whether or not Termina itself is a different dimension or just a nearby land.