Long-time(though not current) Eve player here. Don't forget that, unlike DU, SC, and, to an extent, ED, Eve ships have no interiors. You point and click to fly, mostly, with some manual acceleration control. So, things are much simpler, which is why they could even THINK of attempting a fleetfight with 6k players. Now, here in DU, there's much more going on, so we won't see fleets that large. Probably ever.
Thing is, we won't have to.
when dealing with ships with interiors, multicrew, etc, even a 25v25 fleet action will give you the same feeling, and will be MUCH more visually impressive. So, we'll get that experience..and having said THAT, DU has the benefit of better tech and a ground-up approach that supports this kind of thing. And it only gets better from here. This was not available to CCP when they started. They're in a bind.
My (unsolicited) advice to CCP: Time for EVE 2.0. A game that matches what SC,DU,ED are doing, and attempts to surpass it, because, we are not going back to the current EVE model. It's dead.