GW is pushing small updates to bring all the 40k armies in line prior to Fantasy coming out in 2015. This is an attempt to balance the game out by putting the releases closer together, but it cuts into the budgets of each army production wise limiting the number of things they can update at one time. Once that is done 40k will then switch to a supplement/wave release pattern while the spotlight is focused on Fantasy instead.
That may be what they're doing, but I don't see how it supports the argument for releasing new kits instead of bringing old ones up to date - e.g. Riptide vs revamped Crisis/Fire Warrior kits, Maulerfiend vs Cult Troops and Wraithknight vs every single Eldar special character?
Quite frankly I'd love for our codex to have not a single new unit, but simply to adjust points costs, update rules, shuffle the FoC slightly (through HQ unlocks and Walkers into FA) and resculpt every model over 10 years old.