That's for Salvatore to decide, but the version is just an arbitrary choice. Assuming that Disque is coming as a Redis module, it may be even supported by v4.0. OTOH, I believe that implementing Disque will have implications on the Modules API, so these would have to be backported to a v4.2 (or alike) if it is decided so. In any case, this shouldn't have an impact on the Disque roadmap significantly IMHO.
In the Redis sense, streams are just a new data structure (value type of a key), so there shouldn't be any special concerns with regards to Sentinel, partitioning and/or clustering in that sense.