It might help people to speculate more accurately, if they didn't speculate as if GW2 and it's release date are in a vacuum unaffected by anything else other than the game and it's developers.
A few things to consider:
1.Mist of Pandaria (seriously, if it is not released before this game by atleast a month, then early sales of GW2 will take a huge hit).
2.Marketing and the gaming convention season, as they are one and the same thing (for Arenanet and NCsoft to get maximum impact and exposure this year they need to arrive with a live game).
3.Partially to do with point 1, they need to disclose the release date as close to the actual release date as they possibly can, without negatively impacting sales too much (if they fail to do this Blizzard will do everything they can to rip Anet a new a-hole).
4.Whether people like it or not because it goes against their release date speculations, NCsoft does not like the idea of releasing in September, regardless of how successful they think GW2 will be, I am pretty sure we will not see GW2 released in this month.
5.The ubiquitous Cash shop, believe me this little baby is at the fore front of NCsofts thinking when they consider GW2's release, the sooner they can get the game live and income streaming in via this, the happier they will be (and so will their investors).
6.Mike O'Briens comment regarding people speculating the game would not release in 2012 as being absurd, is really quite informative. It shows that even in their worst possible outcomes that they have listed down, they have a cushion that will still avoid the game pushing into 2013. (Say the worst possible outcome is October, that would leave them a cushion of 2 months still, which is why he was able to say these speculations were absurd).
7.If October is what Arenanet has as their worst case scenario regarding the games release and September is firmly in the naughty book as far as NCsoft is concerned, that leaves us July/August (after the recent announcement of the stress test, which will take place on the 27th June and another BWE to follow, I think the chance of a July release are very low but not impossible).
8.This leaves us with August, in particular the first 2 weeks of August, as the rest of August is convention season (this is maximum exposure for their new shiney toy (what better way is their to boost your sale of your shiney new game, than to highlight it as the conventions, with all the gaming press still in starry eyed and now prompted to keep giving rave reviews).
9. Arenanet stated that the amount of time between the start of Open Betas and release would be shorter than GW (not they hope, but it would be). The first OB for GW was in November 2004, the game released in April 2005 (The mass event prior to November was not a Beta, but a Demo like they have shown at multiple conventions this time around). GW2's OB/BWE's started in April 2012, an October release would be equal to the amount of time GW's took, September is extremely unlikely, due to NCsofts input on the release date. this leaves us with August as the most likely month they would be able to release in and keep that promise. (I am not bothered whether people consider this still relevant or not, because it was removed from the FAQ).
10.May aswell round it off with a number 10 point. The average gap between OB's/BWE/Pre-purchases and the actual release dates of the games for NCsoft is 3.2 months (July 16th), when you throw Arenanets games into the mix we get 4.1 months August 13th).