Howdy James,
I would love to help you with this.
it seemed like you were saying that the RSVP functionality would be in the next version. When will that be out.
It is coming out soon, likely within a month. Due to the nature of programming release dates are mere guesses, and so like other dev shops we try not to publicly guess when something big will be available due to the inherit inaccuracy.
Will that work with assigning a limitation of attendance?
Absolutely.
And can the responses be limited to only logged in WP members?
That is not going to be a feature when the plugin is first released. It will very likely become a feature in the release or two afterwards, as we gauge popular demand for extra features like this and prioritize them accordingly.
Does that all make sense and answer your questions? Please let me know. Cheers!
– Brook