I have no shot as proof but I am 99% positive it was 'next (or upcoming) Week', not week-end. Why should they wait for the week end,makes not much sense, they can announce their decision whenever they want, there is no deadline. Sunday test was chosen (IMO) because the population peaks at weekends and supposedly most players have sunday off.
P.S.
just speculations, but server going live during workdays would MAYBE lessen the initial onrush (day-one craziness) some, rather than when most players are available to log in and play. Sort of mini-ninja event like a fellow poster suggested
