For now I expect McLaren will be very happy filling the holes within existing structure. We know a spider version of the 570S will appear next year and I’d bet everything it will in time do an ultra-light, track focussed version as its answer to the Porsche 911 GT3RS. Before then however it has the rather more pressing business of replacing the 650S with an all new car, currently codenamed P14, and figuring out whether it wants to bite the bait provided by the forthcoming Aston Martin/Red Bull and Mercedes-Benz hypercars and develop a replacement for the P1.
But in the very long term it’s hard to see McLaren continuing to rely on different versions of the same monocoque, engine and gearbox forever. Ultimately I expect an additional front-engined platform will be needed, just because you can so do much more with it: McLaren could make a svelte coupe and a real roadster to slot in under the 570S, but still selling for six figures, and should it ever decide to do a 2+2, it could be achieved without letting the wheelbase get out of control. It would also allow a flagship GT to be developed.
For now however, McLaren is on a roll and deservedly so: its products are world class and the rate of improvement shows no sign of abating. Not bad for a company that launched its first car just five years ago.