Blizzard's stated numbers of MoP's sales was 2.7m after the first week, which included pre-orders and digital sales worldwide.
VGchartz shows that MoP has tapped out at around 950k retail boxes sales, and the weekly sales have dropped off to a trickle. Unfortunately we have no reliable tracking of digital sales, aside from disclosures from source companies themselves.
http://www.vgchartz.com/game/65124/w...s-of-pandaria/ -- 0.94m units total
http://www.vgchartz.com/game/37350/guild-wars-2/ -- 1.42m units total
However, GW2 sold over 1.4m retail boxed sales -- and they're still selling. Arenanet has limited sales in both digital and retail channels to maintain the customer experience (and avoid server boom/bust cycles). If we look at the trending, GW2 is STILL selling ~30k units per week 3 months after launch. MoP on the other hand, is down to ~22k units.
Even if we assume GW2 only has equal number of digital sales...which in today's age is highly unlikely... they're still @ 2.8m. We know GW2 is still selling very well, as new pools of license keys are still being strictly rationed -- for example, Greenmangaming issued a press release when they got a new batch, and it hasn't launched on steam yet.
The most interesting part is that Blizzard did a simultaneous release in all regions -- North & South America, Asia, and Europe.
Guild Wars 2 has not yet had south american nor asian releases. So sales can only continue to grow as multi-regions come onboard.