The 2k Expansion Block has been delivered to backers of the Mega fundraiser from a couple months ago -- check your inboxes if I haven't already caught you online.
The block increases the maximum number of objects of a region from 1,000 blocks to 2,000 blocks. I didn't want to release this previously due to performance concerns, but after the recent performance improvements, I'm looking forward to seeing how the engine handles such demands. If it performs well, then this might be available in the store one day.
PS - Tarkus, if you're reading this, I don't have an e-mail for you, so please get in touch and I'll trade the blocks to your account.