Predictions for job(s) in the next expansion?

[Archwizard]

Spellblade is just in fact a silly Red Mage, if you want to see it, or not.
Its just the other side of the same medal of being a Battle Mage, the Red Mage iteration so far in FF14 is sadly just only a very boring and simple minded concept from a person responsible for it, which seems to believe that as a Battle Mage with roots to Black and White Magic, that you have still to fight mainly like a typical caster far away from second to third row out of safe distance, just to make basically for short moment ala "hit n run very quick short melle attacks.

To say it differently, Red Mage are in fact already Spellblade or Mystic Knights, if they would be designed ad tanks in heavy armory.

Yeah... no.

Every game that has a Spellblade archetype in it also has a Red Mage as an entirely separate job, much as several of the games with Scholar treat Red Mage separately.
Amongst the mixed B/W Casters, think of it as sort of a sliding scale of "Armor and Melee Output" vs "Spell power and selection", with Spellblade and Scholar on opposite ends and Red Mage square in the middle. Point being, you can't really argue 14's Red Mage leans more towards one side or the other, particularly since they historically lack notable aspects of either department.
And that's just the surface level stuff. In terms of actual gameplay, historically, Spellblade often has greater magic defense (even siphoning power from incoming spells) and enemy debuffing power, Scholar offers support skills like Scan and even Item Lore (which is why it ended up as a Healer here), and Red Mage has notably used the boon of faster casting speeds to compromise between its many roles.

I personally am happy with having Red Mages be, well, mages, particularly as they fit the niche of Quick Casters versus BLM's Heavy Caster and SMN's DoT/Pet Caster (which also means a gap open for, say, a more focused DoT Caster than SMN, so SMN can lean into its Pet effects) -- and separately, I'm on board with the idea introducing a Spellblade job under the melee DPS tree, perhaps as a Maiming job to share the Dragoon's knight-like aesthetics and defenses.