To give a long answer to what we know up until now: read this.
Some quotes to immediately answer some of you questions:
Weave updates will not cost anything. The only thing pricey will be the buyable cosmetics.
And as @Sevensreturn said, next week will most likely be an announcement (there is a timer for their next stream on twitch which is a hint that may lead to that conclusiion).
Edit: As well as this confirmation: