There are already alternatives. But no other site has ever managed to attract the traffic that QL does. I still pop in and check on the main alternative, but posts there are around 1 to 10 per day and it has no classifieds section which is what feeds QL.
If you are thinking of setting up a QL like site, I must warn you that without a massive marketing budget, it doesn't mater how technically good it is, it will struggle to find new users. Over the last couple of years I have seen many try, and fail.
Don't let me stop you... go ahead and prove me wrong.