Will this pace be kept?
That’s the plan.
will it be supported by opensource community for long term?
It’s hard to predict the future, I guess that’s why nobody replied to your question yet 🙂 I’m sure it will be supported, because enough people use it. H2 is used in many (open source and commercial) products. Quite many regularly reply to questions in the mailing list. H2 currently doesn’t have many committers, one reason is that the users are generally happy with its features, and because the current development speed is fast enough and the code quality is good enough.
Subscription based support is currently not available, but that’s planned for the future (it always was the plan to provide commercial support at some point). The reason it is not yet available is that H2 doesn’t yet have enough market share to start a company.