Actually what they said was this:
“If you started playing Elusive Targets after ET 14, or if you have missed/failed too many, you won’t be able to unlock all of the rewards. Make sure to aim for the Silent Assassin rating with this Elusive Target if you want to make sure you unlock the prestigious Winter Suit.” Source
“If you started playing Elusive Targets after ET 14… you won’t be able to unlock all of the rewards.”
This could mean one of two things…
A) You had to complete ET 14 to unlock the Signature Suit with Gloves = there’s only 12 more ETs.
B) There isn’t going to be another ET in one or more of the locations, so it’s no longer possible to get those location specific suits.
However, we know option B) is incorrect because there have since been ETs in all six locations. Therefore option A) is the only possibility. Unless that statement in the blog post is a mistake, or the developers have since changed their minds, then there can only be a maximum of 26 ETs.
“Make sure to aim for the Silent Assassin rating with this Elusive Target if you want to make sure you unlock the prestigious Winter Suit”
This statement refers to ET 22, and suggests that if you don’t achieve SA, there won’t be enough after that to get the Winter Suit. In other words, there’s only four more after ET 22 - a total of 26. On the basis of this second statement, it is very unlikely that the first statement is a mistake.
Therefore, unless something changes, there will only be 26 Elusive Targets.