While the announcement of plastic Sisters of Battle is certainly the biggest recent announcement several other pieces accompanied it.
The first of these are the next wave of Codexes to be released, Imperial Knights, Eldar Harlequins and the Space Marine Deathwatch. The Imperial Knights and Deathwatch books are a little disappointing as each could have easily been rolled into another book as each has relatively limited unit options and, in Deathwatch’s case, do not really differ significantly enough from standard marines that they should really warrant their own book. It is also odd for these smaller armies to be updated and given more fleshed out rules before some major factions, namely the Orkz. While the Harlequins fit into a similar slot of low unique unit count and they could be placed in the standard Eldar codex, there is also enough room for them to be expanded upon and, hopefully, for their model line to be expanded that they do warrant a full codex release themselves.
The Sisters might be the most exciting announcement but the newly announced Combat Roster is the most practical. Warhammer 40,000 will finally be entering the 21st century as it gets its own online list builder. This is a standard by this point for many games and 40,000 has been noticeably behind in this regard. The hassle of flipping back and forth between pages to find point values and war gear option will be gone as everything will instead be reachable through one centralized location. It also benefits every army, something few released can say to do, not just those interested in a chosen faction. Imperium, Chaos and Xenos alike benefit. Best of all, it is free.