A road-map is a best estimate at the time, not a promise. You should know that. The ONLY reason we didn't build the 1024 core chip until now is that we couldn't find a customer/investor to sponsor the (~$5M).
It's not a technology issue! If there was a big commercial market for such a chip it would have happened already...(~100 people buying one chip each doesn't count as a market)
For the record, the roadmap you are referring to is outdated. The official one can be found on our website.
http://www.adapteva.com/introduction