Final Fantasy 4 was, and for many fans, still is the best game of the entire franchise. If its director is onboard the Switch, then he's probably making something worth looking forward to.
Buyer beware, though. This could turn out to be as much of a hollow cash-in as Lost Reavers* . He is, after all, someone who stayed behind with Square Enix during a time when anyone who wanted to work with Nintendo was forced out to form separate Nintendo teams like Monolith Soft, 1-Up Studio, Genius Sonority, and Mistwalker.
*Lost Reavers was another third party Nintendo exclusive title that was hyped up as a "secret online game just for Nintendo fans. The perpetrator, Tekken's developer Katsuhiro Harada took full advantage of the Nintendo consumerbase's trust in his previous work, whereupon he crapped out a half-baked experiment and squeezed money out of anyone who thought the game would get any better over time and "support" (funding).