You see people saying left and right they want Red Mage in this game, and Yoshida may have probably hinted it in the Rising, but I've come to question how exactly would it fit in this game. Also, let's just assume its not going to be anything like it is in FFXI, since the FFXIV team is displaying a repeating behavior of giving classic jobs a different flavor.

Assuming RDM will be a dps, let's briefly examine the places each dps job has now:

Dragoon/Monk are melees with high single-target dps. Dragoon has a normal gcd and wears light armor, monk has a fast gcd and wears leather.
Bard/Mechanist are support dps.
black mage/ summoner are casters that have high aoe dps.
When ninja was released, it was a 3rd competitor of melee dps, even more a competitor of monk since it has a fast gcd and wears leather. Now in 3.0, it lost a little bit of dps in favor of aggro management utility, but its not a full support dps like bard and mechanist

In one of the somewhat older live letters, Yoshida said that they are only going to make 2 jobs per expansion from now on. For the sake of balance, I don't believe they will release a dps + healer or dps + tank, it would most likely be dps + dps in one expansion and then tank + healer in the next. Meaning in 4.0 we will most likely get 2 dps jobs. If the Rising is anything to go by, Red Mage and Samurai would be next.

Now if its true that we are getting both Samurai and Red Mage, we would first have to question what role Samurai would take. Again, we are assuming they will not work anything like it did in FFXI. What I'm thinking, is that it would be a melee competitor to dragoon, meaning light armor and slow gcd. That would once again establish 3 melee dps that are fighting for the top in terms of single target dps. Therefore, we can assume that Red Mage will not focus on single target dps.

The next thing is that it would need to fill a role that will balance out what we have so far. We can forget it being a melee dps; since by then we'd have 4 of them. What we also have is 2 support dps and 2 caster dps. SE just released a support dps the mechanist, so, logically speaking, red mage must be a caster! Clearly this would be the answer, right?

Well there's just one problem... It's still a Red Mage. And I speak for every single iteration of Red Mage throughout the Final Fantasy franchise. Red mages are not just black mages with a sword, even though they can cast black magic. Same thing with white magic. Red Mages have always been a jack of all trades job; a Swiss army knife with every tool the party needs - including dps. So with this taken into consideration, this makes Red Mage living up to its glory much harder in a game as rigid as FFXIV. If the FFXIV team and certain people in the community think they've had enough of the summoner complaining & backlash, then they are woefully unprepared for what would happen if they made red mage just another caster.

Don't get me wrong here, I'm not saying all hope is lost. There are some things about XIV's design that could allow enough room for Red Mage to exist.

- It could fill the role of a caster dps and a support dps at the same time, using the exact same stance system that Astrologian uses to either fill the role of a regen or barrier healer. I think this would be the best route to take, as this would simultaneously fit in with the balance of roles (4 melee, 2 support, 2 caster, 1 that can switch between caster and support) as well as allowing Red Mage to live up to its fame without being overpowered.

- They can give Red Mage a weak healing spell. It won't hurt. 2.0 Summoner and 3.0 Paladin have proven this already.

- Just because it would have to fill the caster roll for the sake of balance doesn't necessarily mean that they have to wear cloth and have cast times on all of their spells. A 'spell' could just mean running up to a bunch of mobs and wave your sword, very similar to the way a summoner has to stay with melee range to use Miasma II. If the red mage does in fact use instant cast spells in close range, then they can also utilize meaningful auto attacks (since they do use a sword), which would both separate its playstyle from other casters and match the theme of red mage.

- Additionally, Red Mage having both freecasted and hardcasted spells works on multiple levels.
For one, it would match the kind of mobility that Bard/Machinists have, which is relevant if Red Mage has a support stance. As you all know, BRD/MCH can switch on a casting stance for dps which can be turned off for mobility. RDM doesn't necessarily need to have a stance like this, but instead they can have two different levels of skills (i.e. Dia / Dia II) in which one is instant cast and weaker, as the other one is hardcasted and stronger.
For two, it makes sense as a competitor to summoner. Summoner does a lot of damage through off-gcd skills, as well as having Ruin II, giving them much more mobility than BLM. Red Mage can be very similar to summoner in terms of mobility by having some of their skills instant cast.

- There is also the possibility of competing against Ninja as a mid-level dps.

Keep in mind though, that in 4.0 the caster DPS could be something else and everything I said would be invalidated.