https://www.chabad.org/library/article_cdo/aid/2312384/jewish/Chapter-3-The-World-to-Come-Why-a-Bodily-Resurrection.htm provides a summary of the 2 opinions about Olam Haba, see there for more details.
The Rambam* maintains that the World to Come (Olam Haba) is the World of Souls (Olam HaNeshamos), which is often referred to as the Garden of Eden (Gan Eden). It is from this pool of souls in the spiritual realms that every soul departs when it is about to descend into a body, and it is to this same state that the soul returns when it leaves the body at the conclusion of its mission.6 Ultimately, when the time comes for the Resurrection, this will be (as conceived by Rambam) a transient stage, for after the Resurrection the body will again die, and the soul will return to the World to Come, i.e., to the World of Souls.
Most authorities** Including the Arizal*** hold that the phrase “World to Come” in the Talmud refers to the era of the Resurrection of the Dead in this world. (This state is called Olam HaTechiyah; literally, “the World of the Resurrection.”) The Olam Haneshamos is a temporary place for the Souls to rest before the Resurrection of the Dead.
As with regards to where will Klal Yisrael be when "Hashem will remain on his own on that day"(Isaiah 2:17), The Zohar Hachodosh 164,1 explains That when the Klipa is removed from Klal Yisroel we will be are One with Hashem and therefore we will not be destroyed as we are part of Him.(This requires much more explanation in the appropriate setting)
וכתיב (ישעיה כה ח) בלע המות לנצח וגו', וישתאר קב"ה בלחודוי, כמה דכתיב (שם ב יח) והאלילים כליל יחלוף, וכתיב (שם יז) ונשגב יהו"ה לבדו ביום ההוא, הוא בלחודוי, כמה דכתיב (דברים לב יב) ואין עמו אל נכר, בגין דישתצי חילא מסאבא מעלמא, ולא ישתאר לעילא ותתא אלא קב"ה בלחודוי, וישראל לפולחניה עם קדיש, ויתקרי קדוש, דכתיב (ישעיה ד ג) והיה הנשאר בציון והנותר בירושלם קדוש יאמר לו כל הכתוב לחיים בירושלם, וכדין יהא מלכא יחידאי לעילא ותתא, ועמא יחידאה לפולחניה, כמה דכתיב (דה"א יז כא) ומי כעמך ישראל גוי אחד בארץ.
*Hilchos Teshuvah 8:8. See also: Midrash Tanchuma, Vayikra, sec. 8; Rabbeinu Bachya, Chovos HaLevavos 4:4; R. Yehudah HaLevi, Kuzari 1:109; R. Yosef Albo, Ikkarim 4:30, 33; R. Yeshayahu HaLevi Horowitz, Shnei Luchos HaBris: Beis David 1:16d
**Rabbeinu Saadiah Gaon, Emunos VeDeos 6:4 (end of sec. 47 and sec. 49); Raavad on Hilchos Teshuvah of the Rambam 8:8; Ramban, Shaar HaGmul; Kesef Mishneh 8:2; Shnei Luchos HaBris: Beis David; Chida, Avodas HaKodesh 2:41; Likkutei Torah by the Alter Rebbe, Parshas Tzav, sec. 2 of the second of the maamarim entitled Sheishes Yamim; Likkutei Torah, sec. 1 of the Biur on the first of the maamarim entitled Shuvah Yisrael
***Who holds this view is the Halacha See Igros Kodesh (Letters) of the Lubavitcher Rebbe, Vol. II, p. 66 (footnote). Also see Zohar I, 114a, and III, 216a; Tikkunei Zohar 10b; Tanya, chs. 36, 37. For a full discussion see Derech Mitzvosecha by the Tzemach Tzedek, p. 14b. See also: Shnei Luchos HaBris: Beis David 1:31b; Ramchal, Derech HaShem 1:3:9; Chida, Avodas HaKodesh 2:42-43.