I am hearing that the new ORD Flagship Lounge is on track to open around September 12th. It's looking really nice, and capacity is going to be very large (though we'll see how the expanded access works out!)
The floor plan has been designed to support Flagship Dining, but that won't be there at opening due to ORD's lack of long haul Flagship First in 2018. The speculation is that it will come for Emeralds in the future if BA or CX move departures to T3 (BA is unlikely, but CX is possible). BA's own Galleries First lounge at T5 is tiny, though it is scheduled for renewal.
After the main H/K Admirals Club is completed, which should also be very soon (though there will be minor touch ups that continue), the new L club will undergo a major renovation. It is currently unclear on whether or not it will close during this time, but it seems likely. The plan is for a two-floor club which should have significant capacity. Construction shouldn't anywhere near the 15+ months that H/K has, it should just be a few.
The L club renewal is going to be to serve the additional L gates which AA will have - the new ones under construction to serve E175s, but also the ones AA will retake from B4, NK, F9, and VX as they gradually relocate to T2 sometime next year.