I have some ideas:
1 - About 3 years without any new way to play (wild x standard). We could make something similar a MTG "singleton", or "Pauper", or "Commander" - We need more than a "week tavern"... we don't need a mode that we only play once at week.
2 - U should make online world tourneys. Giving small prizes.
3 - I really love the "naxxramas"/"blackrock" way of get cards from missions. U should give a expansion a year that way.
4 - U should make Classic sets. Changing some cards, so we could use them in "wild" and still have some new cards to play in standard.
People stop playing because there's any news. Just print new cards it's not enough to make people play this card game forever