I think that it will take few months at most, as it is very needed and there is a room for profit for whoever makes a LN node.
I doubt we will see anything in the next 12 months. I would expect implementation from 2019, if we are lucky. Remember how long it took to get segwit. And segwit has become a major disappointment. I am pretty sure the same will be for the lightning network. Chances are businesses will not implement it, therefore adoption will take years. Bitcoin is screwed right now but hey lets hang in there. Maybe a miracle will happen.
LN doesn't need a fork like Segwit, protocol is already ready for it. It is only implementation that we are waiting on.
As for segwit, Electrum and some other wallets and exchanges have already implemented it, it is just that many exchanges and Bitcoin Core wallet hasn't yet. I hope they will soon.