"Terminal" in this case does NOT mean fatal! So relax. A spike that comes from the crown indicates that there won't be further growth from that point. So the plant is working on other options. One is to produce basal growths (not keikis, they aren't independent growths, they share the root system with the main plant so don't try to separate them or you likely will kill both). The other is to produce true keikis such as what you're seeing. It may eventually produce roots and be able to live as an independent plant but don't even think about separating it until there are good roots from it. But it can sit there with a leaf or two or more, produce a spike, and no roots, even for several years.
Phals do reach a point where they stop growing vertically (and produce "terminal spike" - spike at a terminus, not a fatal one). So to look for these other "strategies" ... you have never seen a 2-meter (6 foot) Phal, after all... clearly they have other ways to propagate.
Take a look at this plant of mine,
Phalaenopsis schilleriana prodigy
The leaves up the spike did eventually produce a couple of small roots, but I left it in place and it is producing a spike yet again (along with spikes from the main plant), will be in bloom in a couple of weeks. But that keiki on the stem is now in year 3.
For your plant, just sit back and see what it does, give it the usual regular care.