Hayom Hazeh -- "These are the words of Moshe"; who else would be speaking?

In the beginning of Ki Tavo, there is a transition from the vidui maaser {note: fixed from mikra bikkurim} back to Moshe's instruction. Thus, in Devarim 26:

טו הַשְׁקִיפָה מִמְּעוֹן קָדְשְׁךָ מִן-הַשָּׁמַיִם, וּבָרֵךְ אֶת-עַמְּךָ אֶת-יִשְׂרָאֵל, וְאֵת הָאֲדָמָה, אֲשֶׁר נָתַתָּה לָנוּ--כַּאֲשֶׁר נִשְׁבַּעְתָּ לַאֲבֹתֵינוּ, אֶרֶץ זָבַת חָלָב וּדְבָשׁ. {ס}	15 Look forth from Thy holy habitation, from heaven, and bless Thy people Israel, and the land which Thou hast given us, as Thou didst swear unto our fathers, a land flowing with milk and honey.' {S}
טז הַיּוֹם הַזֶּה, ה' אֱלֹהֶיךָ מְצַוְּךָ לַעֲשׂוֹת אֶת-הַחֻקִּים הָאֵלֶּה--וְאֶת-הַמִּשְׁפָּטִים; וְשָׁמַרְתָּ וְעָשִׂיתָ אוֹתָם, בְּכָל-לְבָבְךָ וּבְכָל-נַפְשֶׁךָ.	16 This day the LORD thy God commandeth thee to do these statutes and ordinances; thou shalt therefore observe and do them with all thy heart, and with all thy soul.

On this, Ibn Ezra comments:

כו, טז]
היום הזה -
אלה דברי משה.

ושמרת -
בלבך.

ועשית אותם -
בארץ.

Now Avi Ezer, Ibn Ezra's supercommentator, gives a rather straightforward and convincing explanation, that Ibn Ezra is simply explaining the transition; that these are the words of Moshe to the Bnei Yisrael, and are not part of the viduy maaser. Thus,

דלא תטעו לומר שגם פסוק היום הזה אומר המביא ביכורים

And so says Mechokekei Yehuda in Yahel Or. Though I admit to seeing the potential for misreading it in this way, and I see from context why one should not err this way, I am having a bit of trouble really trusting that this was Ibn Ezra's motivation. Context makes clear that it is not part of the statement of the person bringing bikkurim; and does anyone seriously suggest otherwise?! Unless we can find something in Rashi's citation in Tanchuma that Ibn Ezra is responding to -- that Rashi says that every day the command should be new to you, while Ibn Ezra is explaining that it is Moshe, back then, speaking and saying היום הזה. Still, such does not really seem to be required.

Add to this Mekor Chaim's statement, though not entirely helpful here. Upon אלה דברי משה by Ibn Ezra, Mekor Chaim says זה כתוב בפסוק ויפגע במקום ובמקומות רבות.

That is, in parshat Vayeitzei, on vayifga bamakom, the patach under the bet represented the definite article, and thus it was a known place. But at this point in the narrative, the place was not yet known. Thus, Ibn Ezra writes there:

[כח, יא]

וטעם פתחות בי"ת במקום -

דברי משה.

והטעם: במקום הידוע היום.

וכן אמר הושע: ושם ידבר עמנו, כי הוא התנבא על ירבעם בן יואש, והוא היה בבית אל.

ואמר לשון רבים בעדו ובעד עמוס ובספר עמוס מבואר.

ועל דרך הפשט לא יתכן להיות

Thus, it reflects a later hand, namely Moshe telling the story, and for Moshe it already is a known place today. This is great throughout Bereishit, but how is this helpful in the case at hand. Surely Moshe Rabbenu is writing chumash Devarim, and giving them their instructions! What does this add, if Ibn Ezra is really saying this? And if there is some deep meaning, Mekor Chaim should elucidate it for us, instead of leaving us in the dark.

If I may, I would suggest an alternate possibility. Ibn Ezra has other famous and controversial comments, about such statements as עד היום הזה. Thus his statement about the first pasuk of Devarim, and the last twelve pesukim of Devarim (as discussed here). That is, that they were written later by Yehoshua.

Here, the pesukim are talking about bringing the bikkurim to the makom Hashem chooses, once they enter the land. Saying that one should perform the mitzvot during Hayom hazeh implies that the command itself was given during a time that one can fulfill it. Did Yehoshua, or someone later, write this instruction?

This, I posit, may be what Ibn Ezra is trying to counter. Again, he wrote:

כו, טז]
היום הזה -
אלה דברי משה.

ושמרת -
בלבך.

ועשית אותם -
בארץ.

By saying that these are the words of Moshe, Ibn Ezra is saying that these are not the words of Yehoshua or someone later. And it is on that day that Moshe is speaking which is Hayom Hazeh. But how does one fulfill these instructions? And this is the rest of Ibn Ezra's commentary on the verse; and this I think shows that my interpretation is correct, over that of Avi Ezer. ושמרת, to keep it, is to keep it in your heart. So that is how you keep it today. ועשית אותם, such that when you enter the land in the future, you will actually perform it.