Well, I'm not so sure keeping it in closed beta would be such a good idea, I mean, as it stands there are some core features in the current build of Foundry, and stress testing is better then only a few people testing it.
As well, it lets us future foundry users get a taste and familiarity with the Foundry system, so that eventually when it goes live, the learning curve won't be there.
I'm sure by the time Foundry hits live, alot of these identified shortfalls will be implemented. Even with the simplest tools, you can see the creative work arounds players are implementing to see their vision for stories. As we get closer to having more tools on par as to what the actual mission designers have, it will be very impressive what Foundry will provide the overall playerbase as far as content.
I truly believe this is the horse that Cryptic should bet on, ensuring not to drop its developement after season 3.