I regressed difficulty against hashrate to develop this prediction model. My only assumption is that hashrate will continue to increase by 3% on average every few days as it has done in the past. Values before mid-July are actual numbers. The smooth line after mid-July is my projection.
The difficulty level will break a million by Thanksgiving. Mining with GPUs certainly won't be profitable anymore. At that difficulty, even an Antminer L3+ with its 504 Mh/s ASICs will only be making 7 to 8 LTCs per month by that time. It will probably take half a year to pay it off. Instead of taking on that risk, isn't it better to just hodl litecoins instead?