We haven't heard anything about a US version yet.
Presumably, as it was said to be heading west after launching in Japan during December 2014, it should be heading across the pond too.
La-Mulana EX is an enhanced version of the 2005 Japanese PC game (translated to English in 2012) for PS Vita. It adds a new monster bestiary, trophies, and online rankings.
Other than that, you're still helping out Professor Lemeza Kosugi, armed with his whip, as he embarks on a very dangerous journey to claim lost treasures.
It's a tough game, and the sight of its ancient cities, caves, and terrible monsters will be burned to your eyeballs by the time you finish. If you ever do.