Saying FF XII-2 is a sequel, is like saying the second Lord of The Rings is a sequel.
I really hate to be the one to break it to you but... it IS!
Personally, I would have loved FF14 to be a massive graphical revamping of FFXI with a similar combat system and design. There's an old phrase that fits which goes 'If it isn't broken, don't fix it'. That being said, one of the best things about Final Fantasy is how it has evolved over time. The awe-inspiring summons from FF7 onwards (later dumbed down to sheer pointlessness in FF12), the spells,the chocobos, the moogles, the airships, the crystals. They've become iconic with the series, and I can scarcely imagine a Final Fantasy game without them. Even FF13 (with its dumbed down corridor gaming style that grates on you after 2 hours) had all of those! Although, granted the chocobos were not ridden.
I imagine one of the trickiest parts of developing an MMO like Final Fantasy is living up to the name. There is a massive roster of games, including some of my all-time favourite games EVER, and you have to balance the godlike power of those gaming avatars with an online environment. For me, FFXI found that balance eventually. Sure some jobs were undoubtedly more powerful than others, but even the meekest class could find a way to perform great deeds above and beyond expectations. And yet, even with all this, there were still great challenges to be had and tougher fights which still relied on cooperation and teamwork.
If they can even bring a hint of this into Final Fantasy 14, this game will be the success they're seeking.