1. There are no plans currently to implement Snapshot isolation that I am aware of.
2. The entry retriever has just been been made available in our latest alpha http://blog.infinispan.org/2014/05/infinispan-700alpha4-is-out.html
If you want an non blocking write with transactions. I can suggest using Optimistic Locking Mode. http://inispan.org/docs/7.0.x/user_guide/user_guide.html#_optimistic_transactions This will provide lock free writes up until it commits in which case all the locks will be acquired at that time, which should be rather short. And we would also detect write skews. This doesn't guarantee other state has changed, but at least for those keys.