Regarding future proofing, I would say that anyone laying single pairs of fibres is already going to constrain themselves when looking to the future. Take 100 Gbps xcvrs as an example: some use just the single pair (2 fibres total) to do 100 Gbps, but others use four pairs (8 fibres total) driving each at just 25 Gbps.

The latter are invariably cheaper to build, because 25 Gbps has been around for a while now; they’re just shoving four optical paths into one xcvr module. But 100 Gbps on a single fiber pair? That’s going to need something like DWDM which is both expensive and runs into fibre bandwidth limitations, since a single mode fibre is only single-mode for a given wavelength range.

So unless the single pair of fibre is the highest class that money can buy, cost and technical considerations may still make multiple multimode fibre cables a justifiable future-looking option. Multiplying fibres in a cable is likely to remain cheaper than advancing the state of laser optics in severely constrained form factors.

Naturally, a multiple single-mode cable would be even more future proofed, but at that point, just install conduit and be forever-proofed.