Way to go, Andrei!
nopCommerce 4.0 will be an awesome release!
Just a small comment on the above.
If you plan to release the official version in 2-3 weeks and release the developer upgrade guide in about a week this means that nopCommerce developers will have only 1-2 weeks to upgrade their extensions, which I believe is a very short period of time.
Please don't get me wrong as we started with the upgrade 2 months ago (which is quite hard with the many changes you did in the last couple of weeks). But in order to convince more and more people to upgrade to the new version then there must be at least some extensions available for it several days after the official release. I don't think that many of the nopCommerce vendors will be able to upgrade and test all their products on time and release their extensions a few days after the official release. We should target code freeze and BETA releases at least 3-4 weeks before the official release next time (especially after such a big release that has a lot of changes).
This is just a constructive comment to make the nopCommerce ecosystem much more stable and provide more confidence in the nopCommerce community.
p.s: There are no bugs in nopCommerce 4.0 ;)