Did Sauron literally anticipate the arrival of the Istari?

Question

In Eregion Sauron posed as an emissary of the Valar, sent by them to Middle-earth ("thus anticipating the Istari") or ordered by them to remain there to give aid to the Elves.

(Unfinished Tales of Numenor and Middle-earth, "Concerning Galadriel and Celeborn")

What is Tolkien telling us here? Is he suggesting that Sauron knew the Istari would appear in Middle Earth at some point and decided to take on the form the Istari adopt?

Gandalf he did not understand. But certainly he had already become evil, and therefore stupid, enough to imagine that his different behaviour was due simply to weaker intelligence and lack of firm masterful purpose. He was only rather a cleverer Radagast — cleverer, because it is more profitable (more productive of power) to become absorbed in the study of people than of animals."

(History of Middle Earth X: Myths Transformed)

Yet in the quote above that I have provided that I used for another question, Tolkien basically says that Sauron can't get his head around Gandalf an Istari and that he doesn't understand him, but if Sauron had anticipated the arrival of the Istari, surely he would know that they were sent to oppose him?

So what is Tolkien implying when he says Sauron anticipated the Istari?

Answer 1

The quote you mention is taken from the chapter "Concerning Galadriel and Celeborn" appearing in Unfinished Tales of Númenor and Middle-earth.

In this chapter, Christopher Tolkien presents (among other writings) an essay with the same title as the chapter. He describes this as "a short and hasty outline, very roughly composed". The text is presented with no modification, but with interspersed editorial commentary (in brackets) and editorial footnotes. With wider context, the quote reads:

But Sauron had better fortune with the Noldor of Eregion and especially with Celebrimbor, who desired in his heart to rival the skill and fame of Fëanor. [The cozening of the smiths of Eregion by Sauron, and his giving himself the name Annatar, Lord of Gifts, is told in Of the Rings of Power, but there is there no mention of Galadriel].

In Eregion Sauron posed as an emissary of the Valar, sent by them to Middle-earth ("thus anticipating the Istari") or ordered by them to remain there to give aid to the Elves. He perceived at once that Galadriel would be his chief adversary and obstacle, and he endeavoured therefore to placate her, bearing her scorn with outward patience and courtesy.

(emphasis added)

It appears therefore that the quoted phrase is part of the original essay. There are several other places in the essay where quotes appear; for example, describing the elves originally inhabiting the forest that became known as Lórien:

These Elves had no princes or rulers, and led their lives free of care while all Morgoth's power was concentrated in the North-west of Middle-earth; "but many Sindar and Noldor came to dwell among them, and their 'Sindarizing' under the impact of Beleriandic culture began."

It's not clear what Tolkien intended the effect of these quoted sections to be; in the appendices to The Lord of the Rings he uses a similar device to give the impression that he is quoting from other annals or books of records.

At any rate, Tolkien does indeed state that Sauron's appearance as an apparent emissary of the Valar is an anticipation of the role of the Istari; but the word has an intended meaning which is not common today:

anticipate: (2) Act as a forerunner or precursor of.

(Oxford Dictionaries Online)

In that sense, since Sauron pretended to do what the Istari actually did over a millennium later, he did indeed anticipate them.

Answer 2

No, I don't think Sauron anticipated the arrival of the Istari, in the literal sense. Him posing as an emissary of the Valar was his original idea. "Anticipation", in this case, has the meaning of one event anticipating the other.

Him not understanding Gandalf, I think it refers to Gandalf's refusal to manipulate the peoples of Middle-Earth for his purposes or having a direct involvement in their matters.