Maybe you could make different format tags hereafter? Say, when I save a deck as Standard now, backend it saves as "standard-ths", when Khans of Tarkir goes out, all Standard decks on the database are updated to "Standard-Theros" (which comprises all cards available in standard until the last day, this is M14-RTR-THS-M15), and the new Standard is only the new current cardsets. (M15+KTK).
Whenever ktk2 and ktk3 are out, they are simply added to current standard. When the next block starts and rotates out Theros Block & M15, you update all standard decks to "Standard-Khans" and so on and so forth.
PROs:
-Standard searches will look only for current standard, preventing year-old, non-representative "Standard" decks.
-Previous Standard formats are adequately represented and not just moved to Extended or Modern, where they are probably not representative nor playable on the metagame.
CONs:
-Needs some database-side processing whenever Standard rotates on all Standard decks. This might be quite resource-consuming depending on the hardware currently available, and would probably need to manual action from @error unless he somehow automates this.
-With time, it creates a never-ending number of "formats" with old standards. Though at a rate of 1 per year, so it shouldn't be much of a problem performance-wise.