Well…
I don’t believe this was never actually said. I believe you may be referring to this:
Or maybe this:
Or maybe some subtle jabs at monetized energy systems, especially in competitive settings, such as when Guild Wars was released with our first iteration of what is, technically, an energy system (about a third of the way down here)
Which, yeah, heavily implies that energy systems (especially monetized ones in a competitive setting) are against their core design philosophy and that they not only wouldn’t be implementing them anywhere in the game but also paints them in a negative light. I’ve seen people interpret this as “well, he meant for the main game (PvP, quests, explore), which still doesn’t have energy systems”, which, nah, I think it is pretty cut and dry from just these posts where Sirrian’s stance on energy systems in general was (is?).
However, in fitting with what @Lyrian stated, they never actually (to my knowledge) ever said “we will never introduce an energy system”. Heavily implied, yes, but also based on the current circumstances, which apparently changed, judging by the ample evidence available in game today. So when they gradually snuck them into the game, even though they felt more and more out of place and felt like kind of a betrayal of the ideals of which the game was founded on at the time (and honestly, still do a bit), they technically never said they wouldn’t do it.
So, attempting to bring this back on topic: As far as the future goes, even if they have expressed disdain for a particular idea, don’t ever count it out completely. They very rarely will commit to saying something will or won’t happen unless they qualify it (eg., “at this time”, “no plans”, etc.), but even if they do, anything and everything is subject to change for a wide array of reasons.
With the next few mythics out of the way, we could very well be entering an era where we continue to get more mythics through “alternate” sources and the previous rules of Mythic acquisition no longer apply. At that point all we could do is hope that any new acquisition method isn’t so overtly obnoxious that it becomes a deal breaker for our individual will to keep playing (which is going to vary person to person). I hope I’m wrong here.