Neonchameleon
Legend
We've seen a lot already. Smite, for example, hasn't been seriously brought down in terms of spell slot efficiency - and the smite spells have been buffed. Chaos Bolt is almost exactly where it was. Arcane Burst has a 66% chance of inflicting a 20' radius helpless condition.You're assuming that those other options won't be brought down. In fact, they kind of already have with the change from Pact to Half casting, which now requires a mindshift. CharOp is now different for the warlock.
And I think that if utterly savage nerfs were planned for all spellcasters they'd be floating that as early as possible while if wide scale spell changes were made to remotely the 3.0 -> 3.5 degree then backwards compatibility would be destroyed.
I'll also point out that if you're suggesting that spell damage and spell effectiveness is going to be nerfed but we've already seen the updated Eldritch Blast rules then the fact that the warlock normally shouldn't be using their standard action to cast a spell in combat for the first eight levels will be even more true. (Warlock optimisation is very easy - just take as few levels of warlock as possible, but there's a lot to be said for a single level for Pact of the Blade in the right build, while two for two invocations can be worthwhile.).