I can see 2 outcomes from what I've read from fighter/wizard design. I base this on [paraphrasing] "fighter will be equal and can shrug off wizard spells at high levels" and statements like "haste etc. will never be as good as mundane fighter attacks" plus the fact that Monte was the Wizard fan, Mearls the Fighter fan, and Monte be gone.
1) Wizard is the recognizable unarmored, 'weak', spellbook-dependent, limited-cast (except for say a feat for weak at-will attacks) class from 1e-3e. This means wizard will lag throughout the progression in combat at least, as he'll definitely start behind everyone at 1st; and at high-level, the best he can accomplish is unloading his full complement and having it shrugged off. Meaning the Ftr beats him bloody at close or long range, prepared or not, any level. Wizard is now a utility class that the others keep around for noncombat uses, and can bully at will. High-level wizards in the campaign world are more like sages - respected for their usefulness but hardly feared. i.e. DM: "Behind the row of orcs stands ... the EVIL SAGE!"
2) In order to come close to balancing the statements made so far about Ftr, wizard is unrecognizable from the 1e-3e Wiz. He wears armor and has high HP and can stand toe-to-toe with the Ftr in melee. OR he has unlimited spells that are all weaksauce or utility-only (shift a foe 5' on failed save, spoil 1d4 food rations in foe's backpack, +1 to all poison saves for 1 second, open unlocked doors, light torches, etc.) OR some other combo that is a departure from 1e-3e Wiz.
And that's fine, many obviously want that. But either option means I'll be sticking to 1e-3e/PF. I daresay the player base will remain very much split.
I think, hyperbole on tour...
The fighter of 2nd edition was able to shrug off most spells. A fact. But there were spells that just didn´t attack the fighter directly.
Defensive spells. Making holes in the ground. Making the ground very greasy, icy or something.
The 2e wizard just had to be more creative than just using direct attacks. In 3e, there was a different tactic: Hey fighter, what is yur will save? Ah, does not matter, you can´t beat the DC anyway. And now you are down two Persons.
Also spells like haste had serious drawbacks: you lost a year of life. So you could use it once in a while, but not as everyday tactic.
So please, stick to any edition, but stop pretending a 2nd edition wizard was as overpowered as a 3rd edition wizard compared to a fighter of the same edition.
Maybe a wizard could lay down a whole army once or twice a day, the fighter held everything together in pre 3e. (And this is from someone that did not like fighters back then.)
Even if a fighter never had a chance to kill the high level (prepared) wizard, against high level monsters, both could hold their own. The fighter was tough as nails. He only needed some kind of armor. The wizard could use spells to enhance the fighter´s performance. Add monsters, that were immune to some spells, 95% magic resistant, and you instantly notice, that wizards and fighters both were needed.
In 3rd edition all those balancing factors were thrown overboard (more or less accidently i guess)
So in 5e I expect saving throws and saving throw DC not scale as in 3e or 4e. I rather expect level bonuses to saves. None to DCs. I expect abilities for the fighter to make saving throws one round later to end effects. Those are concepts explored with 4e and they work great. Often you take out a combatant for one round, but then he comes back. In 4e even skipping one round is terrible, but I remember times, when a ghoul disabled someone for 10 minutes with no chance of recovery. Bad. Really bad.