The Enclave are a devestated organization my friend, there power has gone out in the wasteland. There power was crippled by the destruction of the oil rig and whatever strength they rebuilt in the following thirty five years was smashed in the war in DC. And what you describe aren't the Enclave they don't accept filthy wastelanders into there organization, there more exclusive then the western BoS. Even at the piniacle of there power in FO2 they lacked the military forces to challenge the NCR directly.
I suspect Fallout 4 will be in Chicago. Rothchild mentions there being a small detatchment of the brotherhood there, while as you said ED-E references the presence of the Enclave.
For the enclave to return, they actually need a plot or reason too. They shouldn't just return for a cameo, they should be one of the man organisations of the game if they ever return. Personally, I'd like fallout four to start with the player as a member of the enclave, attempting to redeem the organisation but that's just me.
I had this idea where a Enclave protagonist has to go on the run after finding and putting on a pip-boy containing encrypted classified Enclave data which if decrypted would reveal a deep dark secret that could destroy the Enclave from within.
Why? The Brotherhood had nothing to do with the end of the Enclave in Fallout 2. Enclave in DC are to far away to be in a DLC for New Vegas and have also been destroyed.
The Midwestern BoS on the other hand are in Chicago and they would not know of the Enclave and what they have done for they left before the events of Fallout 2.
They did hunt down Enclave personel who tried to intergrate into the NCR after the Oil rig was destroyed. There's also this dialog.
Spoiler Player: "Is the Enclave's treatment by the Brotherhood influencing your opinion?"
Arcade: "Some of the old-timers like Moreno hold grudges against the Brotherhood and the NCR. I'd like to think I'm above that, but you may be right.
*there discuss where to bring ED-E*
It was cut from the game because Arcade leaves the party after the events of his personal quest so it had little use.
And considering its been only forty some years sense Fallout 2, I think word of the Enclave could have crossed the wasteland. Especially given east coast BoS knew where the MWBoS was.
In any event I doubt the Enclave would play nice with the local brotherhood or vica versa.