I also use a digital camera. I think that, in the digital arena, mirrorless cameras are going to conquer a larger share of the market in the future. That will, in turn, keep the interest for old-time manual focus lenses high. Not just Leica, but anything of good quality.
So my simple crystal ball (dating back to 1980, an analogue one) says that this is not a wrong moment to buy into manual focus lenses because second-hand prices are not going to diminish in the "crystal-ball foreseeable" future.