What do the coming verses discuss?
Rashi (Tehilim 96:1): It is about the future ? "Ki Va Lishpot Es ha'Aretz" (33).
Radak (here and Tehilim 96:1, 105:1): David composed it 1 when he brought the Aron from Beis Oved Edom, together with Mizmor 105. The coming 14 verses are essentially Tehilim 96. The previous 15 verses are essentially Tehilim 105:1-15. For 43 years, they sang the previous verses in front of the Aron in the morning, and the coming verses in the afternoon, until Shlomo brought it to the Beis ha'Mikdash (Yalkut Shimoni Shmuel II, 142). Radak (28) ? it discusses the wonders that Hashem did via the Aron, and also the future, when He will take us out of Galus. Then, all Goyim will honor Him ? "v'Hayah Hashem l'Melech Al Kol ha'Aretz" (Zecharyah 14:9), and it says here "va'Yomeru va'Goyim Hashem Malach" 2 (31).
Malbim (here and Tehilim 96:1): It discusses Hashgachas Hashem via nature, He does hidden miracles to save Yisrael, and for the success of His servants and lovers. Here it adds wonders that Hashem did via the Aron when it was in Eretz Pelishtim. Through this, the nations recognized His wonders, and that all gods of the nations are not G-d.
This is unlike Radak (91:1) brought from Shocher Tov, that Moshe composed all the Mizmorim from 90 until 101.
Radak (28): Also, it says "Yir'am ha'Yam u'Mlo'ah" (32), and it says about the gathering of exiles "he'Harim veha'Geva'os Yiftzechu Lifneichem Rinah v'Chol Atzei ha'Sadeh Yimcha'u Chaf" (Yeshayah 55:12). Then they will say to each other "Hodu la'Shem Ki Tov Ki l'Olam Chasdo" (Tehilim 118:1).
Why does it say "Kol ha'Aretz"?
Radak (Tehilim 96:1): "Kol ha'Aretz" refers to all the residents, like "v'Chol ha'Aretz Ba'u Mitzraimah" (Bereishis 41:57). Malbim (Tehilim 96:2) - now, most Nochrim deny Hashem. They attribute the entire creation to stars and Mazalos. (Then, all will admit to Him.)
Why does it say "Baseru"?
Radak (Tehilim 96:2): Even though all will know the salvation, it will be dear in their eyes every day as if it happened then. Besorah is a new tiding; it is dear to a person the day that he hears it. Afterwards, its dearness diminishes. This Besorah will be different.
Malbim (Tehilim 96:2): Besorah is not for a common matter, e.g. that it became light in the morning. It always happens and must happen! Besorah is for something that does not come regularly. The verse teaches that also His constant salvation every day, taking out the luminaries, will be a Besorah, for it is not inevitable; it depends on His desire to renew the creation each day.
What is "mi'Yom l'Yom"?
Radak (Tehilim 96:2): It is constantly, every day.
