To answer the question of the last traditional turn-based Square RPG I've played, I don't think there's been one since FFX that I've played (have there been any, other than the aforementioned Last Remnant? [I haven't gotten around to that one]).
Anyway, I've not really touched the Gameboy SaGa games (I think I may have dabbled a bit in one of them, but way too long ago to remember). The Romancing SaGa games were what broke my foolish thought that all of Square's games that didn't get Western releases were robbed from us and were actually probably amazing things - I got fan translations of 1 and 3 and didn't like the games at all. SaGa Frontier did nothing for me and Unlimited SaGa just seemed to encapsulate a whole lot of things that I can't stand in games. I can't blame anyone for liking the series (everyone has different tastes... I can't stand TRPGs and lots of people love them), but I, for one, am happy to see Square trying a totally normal classically styled RPG since they've not done one in so long. Completely ignoring the name, I'm far more excited about this (graphics be damned) than if they'd done another entry in my least favorite series in their lineup.