Hello and welcome to the forums!
Glad to hear that you're enjoying the game already. Let's see about these questions:
1) There is no set date yet, the closest I can give is "several months". We've posted announcements about soft launch both on the Forum here and on our Facebook page.
2) Clans are not in the game yet, though they are being worked on!
3) We do have a Facebook page: https://www.facebook.com/RaidShadowLegends/ Twitter also exists but it will be used later.
4) Definitely! Keep in mind that the first ones will focus on fixing bugs and immediate issues, extra content will come a bit later. But I've already asked the Devs to provide a Roadmap that can be posted on the forum. This will be done as soon as they have finalized a few steps in the plan!