The tweet + approach is probably sufficient to bring a lawsuit and get into discovery and then it'll come down to if there's a smoking gun documents (e.g. internal emails comparing the voice to Her, etc.)
It's likely that someone internally must have noticed the similarity so there's like some kind of comms around it so it very much will depend on what was written in those conversations.
You can time the election for when you think it would be optimal for you. (e.g. a summer month will mean students will be at their parents which swings university cities more conservative)
Following IBM's acquisition of Hashicorp the moves seems unsurprising, they wouldn't want to be beholden to a competitor.
We'll inevitably see others large companies follow suite - it was one thing when hashicorp was independent tech company but it's very different when it's owned by a direct competitor.