Look at the damage those spells are doing. Even in a 9th level spell slot, a fireball or meteor swarm only does 12d6 damage (avg. 42). A 9th level magic missile does 11d4 +11 (avg. 38.5) That's only about as much damage as a fighter can do at-will, and that's using the one and only 9th level spell slot a wizard gets per day! It's pretty sad when a 9th level spell can only rival the at-will damage of another class. Yes, I know this can hit an area, but still. This is the best a wizard can ever do, and he can only do it once per day. 15 out of the 19 total spells a wizard gets per day are 1st-5th level; only 4 spells per day are 6th-9th level. All of those lower level spell slots will do even less damage. So right now, high level wizards can't even compete with a fighter's at-will DPR, let alone a fighter's damage with action surge!
DnDN has 3e-like hit point scaling but has cut the damage of spells at higher levels by up to half or more. Meteor Swarm, for example, used to do 24d6 damage; now it does 12d6. People complained about how much blasting spells sucked in 3e, since they did the same damage they used to do in 2e but hp had greatly inflated. Well, this problem is far worse in Next. Plus, fighters now get 4 attacks per round but their attack bonus is no longer reduced by -5, -10 and -15. So those attacks are all far more likely to hit, giving the fighter an enormous DPR boost in this edition. So, no, I'm not at all worried that a nerfed action surge would make fighters weak compared to casters.