FF7 is a sci-fi game, and it's not a simple game to understand.

That being said, you already played the original. If you aren't looking for 100% comprehension (i.e. you're OK with missing a bunch of details half the time), then it can definitely done, even in less than a year. I've been studying for around... 8 months? I'm halfway through core 6K, and I'm fighting my way through FF7. Do I understand everything? Absolutely not. Can I play it and follow most things since I already know the plot? Yes. Do I even understand some things better than I did in the original translation, due to it being deeply flawed? Also yes, but very rarely. Most of the time even the terrible translation is better than my understanding.

If you're looking to fully understand it, on the same level that you understand the English version? That's probably not going to happen in a year.

But honestly man, if your only reason for playing it in Japanese is disliking the dub voices? The game is likely going to have the Japanese voices available. FF15 did. And if you're willing to wait a year, then you're basically willing to wait until the PC version comes out, and that will DEFINITELY have the Japanese voices, via mods if nothing else.

So my summary is this, TL;DR:

You cannot experience it on the same level that you would experience the English version. Depending on your definition of "passable comprehension", you might be talking about something very possible, that could be done even in six months.