The full release notes are on the Arcen forums. This is another big mix of stuff for the CoN expansion and the base game.
Overall, this release is a human-player-focused one, whereas a number of the recent updates could have been described as being more AI-favoring. There are six new warheads added in this version, all within three existing lines, but one of those lines with additions is the nuclear warhead line.
What on earth could be more powerful than the nuclear warhead, you might ask? After all, it literally destroys a planet and all its resources, while obliterating most ships on the planet (Mark V ships and starships being the main exceptions), and it does so for a whopping +50 AI Progress (that's bad). What on earth could a Mark II version of that warhead add, let alone a Mark III? You can check out the release notes (or the beta) for full details, but the Mark III version is nicknamed the Doomsday Device and carries a +5000 AI Progress cost to it for a reason. Bwa ha ha...
Those are now part of the base game, and so are the new Mark II Transports. Perhaps these are less dramatic than the mega-destruction-warheads, but they are still really exciting. The Mark II transports are uniquely useful because they actually slowly regenerate all ships stored inside themselves. This actually makes for some pretty interesting abilities to support fleets on deep strikes, although the regeneration is very slow for all ships except Neinzul Younglings, which are regenerated in these at the same rate as a Regeneration Chamber (but they don't automatically seek these out or get ejected from these). For players who are playing with the CoN expansion and suddenly get a new Neinzul Youngling ship class late in the game, if they had not already unlocked the higher-level Enclave Starships then that Youngling ship class could prove to b useful only in defensive situations (because they are too short-lived to be used offensively without some sort of support). The Mark II Transports now provide an alternative, much knowledge-cheaper way to support Younglings on deep raids.
Also new to the base game: Mark II and III metal and crystal harvesters have been added. These only add a little bit of income per harvester, so are mainly helpful for players who already have a lot of territory, but they also drastically reduce the rebuild time for harvesters, which can also be immensely useful for protecting the resource flow of players who keep losing a lot of harvesters in raids.
Specific to the CoN expansion, there are now Neinzul Silos and a new Neinzul Rocketry Corps minor faction. These are reminiscent of parts of the Battle of Briton, with V2 rockets coming in to the allied airspace. Only this time it's aliens launching lightning warheads and occasionally EMPs from AI planets at the humans. Don't worry, there isn't an AI Progress increase from those incoming hostile warheads -- the fact that your enemies are now using at least a few warheads for the first time in AI War history (which is another longstanding player request) is bad enough!
The Neinzul Viral Swarmers have also been nerfed quite a bit (not before obliterating some adventurous beta testers, unfortunately), and we fixed a bug with the Hybrid Hives in the last beta version that was preventing any from spawning (whoops!).
There are a number of other minor fixes and additions, too, and you might notice that your EMP and Tachyon Warheads now pack a little extra punch, too. Enjoy!