Depends whether by ‘true’ you mean it was wrong then and still wrong now, I guess.
Multiboxing is effective in certain tasks, like mining or ganking or running some fixed scenario sites. And there’s a certain portion of any player base that’s willing to go to the lengths of multiboxing (as Syzygium said, let’s call this more than 2-3 accounts) in order to maximize rewards.
That portion of the player base will never be more than about 10-20% simply because most gamers can’t be arsed to put that much effort into their games. And it won’t become ‘dominant’ or be unbeatable for the same reason that large corps and fleets never became dominant or unbeatable. Too much of the game is still basically soloed. And CCP could/should modify content to become less box-friendly, they just don’t want to cut into their income.
And the whole “paying players are subsidizing multiboxers” trip you tried to go down was just nonsense.
But yeah, sure, for negative values of ‘true’, your prediction came true.