The Steel Wind Strike spell description says (XGtE, p. 166; emphasis mine):
You flourish the weapon used in the casting and then vanish to strike like the wind. Choose up to five creatures you can see within range. Make a melee spell attack against each target. On a hit, a target takes 6d10 force damage.
You can then teleport to an unoccupied space you can see within 5 feet of one of the targets you hit or missed.
The way I read this follows as such: it says "you can" do this, and therefore it is a suggestion rather than a requirement.
However, I know the intent of the spell is to be essentially teleporting after every strike. The intent was derived from a tweet from Jeremy Crawford, which may change my interpretation to RAW vs RAI:
If you cast steel wind strike, the spell doesn't make you invisible during its attacks. You do vanish from your starting location, as you start teleporting around the battlefield, but you blink into view as you make each attack and then teleport to your final destination.
Am I correct in my interpretation that you don't have to teleport next to a target after your last attack from the spell?
Please let me know how I can determine in the future the emphasis for cases such as this, with a citation from a book if possible.
Best Answer
No. You do not have to be in any particular location.
There is unlikely to be a citation specifically for this case. However, the general rule in 5e is that with only a few exceptions, things are designed to be as close to natural English language as possible.
If it says "can", that is because it is optional, as is the case in natural English language. If you choose to take advantage of this option, then you will teleport to a space within 5 ft of one of the targets. You can choose not to teleport, or you can choose to teleport and then use movement to move beyond 5 ft. Nothing in the spell requires you to use that teleportation.
The obvious flavour of this spell is that you are in fact teleporting around quickly attacking everyone, but the mechanics don't require that to be the case. You can choose to remain where you started at the end of casting the spell. Within the intended flavour of the spell, imagine this as teleporting around attacking everyone, and at the end teleporting back to where you started.