I still have no numbers to extrapolate but assuming a whole Wikipedia with millions of articles parsed as meme pool in an RDF structure will need terabytes of RAM then probably memory bandwidth will be the bottleneck for the SPARQL queries. Currently we have up to 64 cores with 8 DDR4 channels with each ~25 GB/s on a single socket system, IBM's enterprise server may have a bit more throughput, but I guess until we have some kind of 1:1 ratio for cores:channels Tummi won't be able to query the whole Wikipedia in reasonable time...still some time to pass.