We know the next Event will be a late-June Whitestrakes Mayhem - yes, it's very soon after the one we had in May, but that particular one (May Mayhem... May-hem? Surely that pun is worth re-using sometime) really should have been in February.
But what after that?
Two events, of course, are pretty much set in stone. Witches Festival (around Halloween) and New Life (Christmas and New Year). But what else?
I've heard rumours of another Zeal of Zenithar, but so far that appears to be only player rumour.
We have never yet had a Blackwood event that included the Deadlands (Dagon-themed most likely, "Fire and Flood"), or a High Isle event that included Galen (Druid / Breton "Nature's Wrath" theme?) So I would expect at least one of the events later in the year to have one or other of thse themes.
It's been a LOOOONG time since there was a Murkmire event, or any chance to get the seven-part Grave-Stake Memento.
It's been an EVEN LONGER time since there was a Thieves Guild or Dark Brotherhood event.