Nikon has been a profitable company year on year for as long as I remember. They certainly have more cash piled up now than they had when they developped breakthrough products such as the D3, another time when mode internet forum experts had declared then death and buried. 
So there really is no reason to doubt their ability to invest.
Last time I checked, Nikon were operating at a loss.
There's much more to being a successful company than having the best current product. Otherwise Betamax would have prevailed over VHS.
Besides, the 1 series has proven their mastery of on sensor AF, what are they missing really?
No, it means that they could keep up with Sony's first-generation systems (the A7r didn't even have PDAF, while the A7's was rudimentary), and Canon's technology at the same time, four years ago. While using lightweight lenses on a 2.7x crop sensor that didn't require nearly as precise focusing as full-frame and APS-C sensors.
The difference in level of precision required makes it similar to you saying that two marksmen are equal because one can hit a 1m-wide target just as quickly and consistently as the other can hit a 30cm-wide target.
They haven't released anything since, and the AF performance of Nikon's SLRs in live view mode is woeful in comparison to current Canon models with dual-pixel technology (particularly when using STM lenses), let alone Sony mirrorless cameras.
Also, unlike both Canon (on video cameras) and Sony (on the A9 and on video cameras), Nikon has yet to demonstrate a lag-free EVF or live view system, which is required for action photography on a mirrorless camera.
I'll tell you, the one and only thing they have been missing is the intention to compete in the mirrorless high end market. Why? Probably because some decision makers in Nikon didn't want to canibalize their DSLR sales... yet... Now that Sony is deservedly eating away big chunks of their market Nikon has no more reasons to hesitate, do they?
It's not hesitation. More likely it's because they haven't got the capability to compete.
Nikon and Sony have been taking big chunks from Canon's market share for years, due to their low-ISO weakness. At low-ISO, the 5D3's shadow areas were a mess of horizontal lines. It took them until 2016 to respond with the 1Dx2 and 5D4 - full-frame cameras capable of low-ISO performance in the same ballpark (if not quite up there) with the leaders. And Canon's a much larger and better-resourced company than Nikon.
Besides, I believe that Canon will follow suite, but probably one year later (too late?).
Why would Canon be later?
Their
demonstrated mirrorless AF capabilities are far more advanced than Nikon's and they have a more mature mirrorless-capable lens motor system (the STM lenses) which can easily be added to the next generation of L-lenses.
Moreover, unlike Nikon, many of the key Canon L-lenses are older than their Nikon counterparts and due for an update anyway. The 24-70 and 70-200 could be updated tomorrow, with improved optics as well as stepper motors, and it wouldn't be out of place in the product cycle. Same with many of their supertele lenses.
It would make sense for the 5Ds2 to be Canon's first mirrorless full-frame camera. Canon has already lost much of the high-resolution, non-action SLR market anyway (owing to their inability to compete with the D800/D810 and A7r/A7r2), so not a lot of candidate buyers will be carrying a large lens collection across. As a high-resolution, slow-shooting non-action camera, which, most likely, will be able to stand against Exmor sensors DR-wise for the first time in ten years, it is an ideal candidate to launch a new line of mirrorless cameras and lenses, or even a new lens mount - even if it doesn't match the A9 (or successor) AF-wise (understandably, since Sony has such a head-start in mirrorless), it doesn't particularly matter for most non-action shooters anyway. This could then be followed up with balanced, speed-focused and entry-level successors.
For Nikon, the entry-level route makes more sense than the high-end/high-resolution route. Nikon already half-owns the high-resolution scene (split with Sony), so many users would be carrying a lot of lenses across to the new system and would be understandably reluctant to have to replace them. But the D610 also needs a successor, and APS-C bodies are in constant need of successors. Users of these cameras often don't have a lot of lenses to carry across, or are stepping up from various small-sensor or fixed-lens cameras, so would have to buy new lenses anyway - an ideal place to launch a new mount and lens lineup.
