They'll introduce rules for Sanguinius when they cover Signus Prime in the HH rulebooks. Then hopefully it won't be too long before we see the model of him. Especially now they more than one sculptor working on the Primarchs. Before they make a Magnus model they will be doing Night Haunter, Perturabo, Corax, maybe even Alpharius/Omegon. The next HH rulebook will cover some side-battles before moving on to the big ones like Signus and Prospero. It will cover Imperial Army, Imperial Knights, Mechanicum, plus some Iron Warriors.
I'm hoping they bring him out before then. Hopefully they do Signus Prime After they wrap up Isstvan V. I'm assuming that the remaining Primarchs that were present at Isstvan will be released before they mve on and progress the story. Signus Prime could introduce Sanguinius, The Fall or Prospero can introduce Leman Russ and Magnus, Could then do the Battle for Calth to get Guilliman in Before heading of to Terra and bringing in Dorn and Khan. Just need to squeeze in the whole fall of the Dark Angels in as well to get The Lion on board somewhere along the line.
Forge World does indeed have some nice models but as a vanilla Tau player they don't really offer me many useful blueberries.
Night Lords Legion Contemptor. http://www.forgeworld.co.uk/New_Stuff/NIGHT_LORDS_LEGION_CONTEMPTOR_DREADNOUGHT.html Iron Warriors Legion Contemptor, http://www.forgeworld.co.uk/New_Stuff/IRON_WARRIORS_LEGION_CONTEMPTOR_DREADNOUGHT.html
Best part of Forge World, the cosmetic redesigns for Imperial Guard and their vehicles. I also like how Forge World has implemented much of the Heresy technology for players to use and also the fact they have Titans even though most of us wouldn't spend that much money on one unless you were really really bored and wanted to just cash bomb them. Best thing about them though are definitely some of the terrain cosmetics they've designed.