Yes, the plan is to have a whitelist of SPARQL endpoints for which we allow federation queries. I was going to post about it in January when everybody's back from vacations :)
I'm very curious to see how this will fare. Federation is where I think public SPARQL endpoints will fail, so it will be worthwhile to see what happens.
The use case for LDF is both running long queries and federation. The first use case of course would benefit from good SPARQL engine running on a machine with decent connectivity. So server-side JS or Java should probably fare better.
Actually, probably not: – The V8 JavaScript engine is as fast in the browser as with Node.js. Furthermore, query execution in the browser happens in a background worker, and the UI has been designed for minimal impact. – The Java implementation is based on Jena, which is an engine built with very strong assumptions that do not necessarily hold for TPF.
The main impact I see is latency (California <=> Europe), which can be mitigated with caching and/or HTTP/2.
Best,
Ruben