I can't guess the future, but where it is right now I am using 1200 watts non-stop and paying 7.5 cents a kWH.  This works out to U$D 2.25 a day.  The price is going for around 70 dollars a coin and I am getting .12 BTC per day at BTC guild.  So that is nearly 8 dollars a day on 2.25 in electricity.  I expect the difficulty to continue increasing and if the price stays where it is I will probably be throttling back when the summer heat hits in 2-3 months.

I might look into LTC, but it sounds like it needs even more electricity than BTC.  I think ASICs are the future, but we need more competition if bitcoin is going to stay widely dispersed.