Composer will be an always evolving product to which we think we’ll always be adding.
However, our plan is to get Composer out of beta in Q3/2014.
There will always be a free tier of Composer for you to build and distribute your apps.
We want to see as many people getting innovative with apps as we can. That means we'll base our pricing tiers on the value each user extracts from the product.
If you decide to discontinue your Composer account, your apps will be availble for you to download and work with as you please.