only the beginning

 שִׁיר הַמַּעֲלוֹת לְדָוִד שָׂמַחְתִּי בְּאֹמְרִים לִי בֵּית ה׳ נֵלֵךְ.

 עֹמְדוֹת הָיוּ רַגְלֵינוּ בִּשְׁעָרַיִךְ יְרוּשָׁלָ͏ִם

Radak  learns that the second pasuk here is written in anticipation of the future, like the first pasuk.  Even though it uses present tense, it is  עבר במקום עתיד.  R' Menachem Mendel of Vizhnitz, in his She'eiris Menachem, however, explains that the mizmor is grammatically accurate -- there is a mix of present and future tenses together.  It is speaking about the time when Yerushalayim is in our hands, present tense.  It's a time when we could celebrate Yom Yerushalayim and appreciate our capital city.  But what David haMelech celebrated is that we did not stop there and say, "Mission accomplished."  Yom Yerushalayim was not the end of the story or chapter, but was only the beginning. The celebration of the present was paired with a yearning for the next step, for say בֵּית ה׳ נֵלֵךְ, future tense, but let it come speedily in our days.