Personally, I think it's just a quick bump in activity to keep the natives from becoming too restless. That's my bet anyway, and having asked several questions here and in feedback forms on the Herald already and having got nothing like a complete answer...I see no real reason to think otherwise.
Both Draconi & Leurocian share the same tag here on the Forums, namely Lead Designer, and since Draconi stated they have different duties, that would seem to indicate they each lead different teams, but we really have no other info to support the notion that there's now a full production & development team working exclusively on UO.
Perhaps there is only one team working on both UO & DAoC now.
I suspect the majority of 'NEW' content we have seen, including the Magincia Invasion, was/is already in the can and had been for sometime, most likely part of the initial plan building up to the release of Stygian Abyss. That would go some way to explain why these events seemed to end with no final outcome...several unfinished scenarios, unable to have the original planned endings because the punchline, Stygian Abyss, was removed from the plot.
According to info I was told in a couple of PMs by a former and very well known and respected Developer, who only recently left the UO team, there's almost enough SA stuff already prepared for an expansion pack as it is, so I guess they can serve that up to us piece by piece for quite a while as 'New' content without requiring much of an extra investment.
Mini events like Valentine's Day are meaningless fun for a day or two I guess, but not exactly anything of enduring substance.
The fact is that most people will accept that all is well and as it should be in UO, development & support wise, whenever a Dev says anything at all. Somehow if a poster here has the VIP badge and _EAMythic next to their username, a lot of us accept without question that they automatically speak the truth, the whole truth and nothing but....blah, blah, blah. Historically, that view is not supported by the evidence, but is guaranteed to get a lot of plaudits and kudos from many fawning fans on these forums so why wouldn't EAMythic keep on serving it up, as long as we keep swallowing it?