<PERSON>'s wisdom was vastly diminished compared to that of <PERSON> the Maia (<PERSON>).
<PERSON> says this of the nature of Ainur, comparing the glory of King <PERSON> at his peak to the inhabitants of the West .
In Beleriand King <PERSON> upon his throne was as the lords of the Maiar, whose power is at rest, whose joy is as an air that they breathe in all their days, whose thought flows in a tide untroubled from the heights to the deeps.
-Page 59,The Silmarillion
So we can expect that as one of the Ainur who had participated in the Song of Creation, <PERSON> had great knowledge of the workings of the Arda and some limited foreknowledge according to his stature on <PERSON>'s grand plan for Eä and of the events that were to come to pass on Middle Earth.
However late into the third age when the Maiar who would later become the Five Istari were called upon to journey into Middle Earth to lead the resistance against the growing power of Sauron, they were required to give up most of their Maia powers and take up mortal forms to dwell among the inhabitants of Middle Earth. Undoubtedly though their wisdom was far superior to that of an ordinary mortal, their taking up mortal forms had come at the cost of a surrender of their natural Maia state of mind.
It was resolved to send out three emissaries to Middle-earth. 'Who would go? For they must be mighty, peers of <PERSON>, but must forgo might, and clothe themselves in flesh so as to treat on equality and win the trust of Elves and Men. But this would imperil them, dimming their wisdom and knowledge, and confusing them with fears, cares, and weariness coming from the flesh.' But two only came forward: <PERSON>, who was chosen by <PERSON>, and <PERSON>, who was sent by <PERSON>. Then <PERSON> asked, where was <PERSON>? And <PERSON>... 381
asked what <PERSON> would have of him. <PERSON> replied that he wished <PERSON> to go as the third messenger to Middle-earth... But <PERSON> replied that he was too weak for such a task, and that he feared <PERSON>. Then <PERSON> said that was all the more reason why he should go...
-Page 393, Unfinished Tales
Thus we can conclude that the wisdom and foresight of <PERSON> while being vastly superior to all but the greatest among the Men and Elves was still greatly diminished when he came to Middle Earth. His ability to see into the future would have correspondingly been limited by the constraints placed on his earthly mind. 381