ExileCon is the jumping-off point for Path of Exile 2's marketing. We'll also be showing it at Gamescom and PAX West with playable demos, so its beta is still a while out. You'll find out all the dates at ExileCon in July.
Btw we've previously mentioned that there is a Path of Exile 1 expansion launching a few weeks after ExileCon and a lot of people are speculating that it's secretly the start of the Path of Exile 2 beta. Just wanted to clarify that that's not the case.