kislev - month of geulah

Meant to post for Rosh Chodesh Kislev, but better late than never and it's good the whole month anyway.

The navi Zecharya (ch 7) raised the following shayla in the month of Kislev:

וַיְהִי בִּשְׁנַת אַרְבַּע לְדָרְיָוֶשׁ הַמֶּלֶךְ הָיָה דְבַר⁠ ה׳ אֶל⁠ זְכַרְיָה בְּאַרְבָּעָה לַחֹדֶשׁ הַתְּשִׁעִי בְּכִסְלֵו.

 וַיִּשְׁלַח בֵּית⁠ אֵל שַׂרְאֶצֶר וְרֶגֶם מֶלֶךְ וַאֲנָשָׁיו לְחַלּוֹת אֶת⁠ פְּנֵי ה׳

 לֵאמֹר אֶל⁠ הַכֹּהֲנִים אֲשֶׁר לְבֵית⁠ ה׳ צְבָקוֹת וְאֶל⁠ הַנְּבִיאִים לֵאמֹר הַאֶבְכֶּה בַּחֹדֶשׁ הַחֲמִשִׁי הִנָּזֵר כַּאֲשֶׁר עָשִׂיתִי זֶה כַּמֶּה שָׁנִים.

Would he have to fast the upcoming Tisha b'Av?

Radak provides the context:

כי עדיין לא היו מאמינים בבנין הבית מפני האויבים שהשביתו את המלאכה כמה שנים ועתה אף על פי ששמעו כי היו בונים היו קטני אמנה ולא היו רוצים לעלות מבבל כי לא היו מאמינים שישלם בנין הבית ויעמד מפני הצרים אותם ושאלו אם יצומו בתשעה באב כמו שעשו שבעים שנה

The rebuilding of Beis haMikdash had started, but the enemies of the Jewish people had caused work stoppages.  It looked far from certain that the project would ever come to completion.  The vast majority of the Jewish people remained in exile in Bavel, waiting to see what would happen, uncertain as to what the future might hold.  

Zecharya wanted to know whether the fact that there was at least something of a Mikdash standing was enough cause to suspend the fast of Tisha b'Av.

Why did he raise this question in Kislev, months and months before it would be relevant l'maaseh?  Why not wait until the three weeks, or some other time closer to Av? 

The Midrash writes at the beginning of Behaaloscha that Aharon was upset because he was left out of the chanukas haMishkan, as all the nesiim brought gifts and korbanos and he did not participate.  Hashem responded that his portion is even greater, as he is tasked with lighting the menorah.  

Ramban explains that the lighting the menorah in our homes in celebration of nes Chanukah is a continuation of the mitzvah of hadlakas menorah.  Aharon's mitzvah of menorah thus continues even after the churban, while the mitzvah of offering korbanos is no longer practiced.  

R' Noson Gestetner writes that when Kislev rolled around, Zecharya sensed the future holiday of Chanukah that would come in 200 years.  Even though he knew there would be a churban ha'bayis of the second Mikdash, he saw in Chanukah a spark of geulah, a spark of the Mikdash that would remain, as the mitzvah of menorah is still with us.  Since the geulah of Bayis Sheni would not completely be extinguished, he wondered whether Tisha b'Av would still be necessary.