Ok,
I realize that what I posted above may not pertain to the question of whether a Jew may remain in Galut, but it does discuss the fact that some Jews may seem to be lost to assimilation and then realize their mistake and do teshuva...
But here is something which I will look into further...
http://www.ravkooktorah.org/BECHUKOTAI_65.htmThe Torah warns us that if we fail to listen to G-d and keep the mitzvot, we will be punished with famine and war, and ultimately, exile.
"I will scatter you among the nations, and I will unsheathe the sword after you. Your land will be desolate, and your cities in ruins." [Lev. 26:33]
The Purpose of Israel in their Land
Why should the Jewish people be punished with exile? To answer this question, we must first understand the true significance of residing in the Land of Israel. If the goal of the Jewish people is to bring ethical monotheism to the world, would their mission not be more effectively fulfilled when they are scattered among the nations?
There is, however, a unique reason for the Jewish people to live in the Land of Israel. They need to dwell together in the Land so that there will be a nation in the world upon whom G-d's honor rests; a nation for whom divine providence is revealed in its history and circumstances; a nation that will be a source for all peoples to absorb knowledge of G-d and His ways. Their goal is to demonstrate that divine morality can fill an entire nation - a morality that enlightens not only the private lives of individuals, but also guides the public paths of nations.
For the Jewish people to fulfill their national destiny, G-d's seal must be placed on the people as a whole. The nation must recognize its special mission as G-d's people living in His land. When the Jewish people as a whole abandoned G-d, even though many individuals still kept some of the mitzvot, the nation had lost their distinctive mark. The land was no longer recognizable as G-d's land, and the nation was no longer recognizable as G-d's nation. They saw themselves as a people like all other peoples.At that point, the Jewish people required exile. They needed to wander among the nations, stripped of all national assets. During this exile, they found that they are different and distinct from all other peoples. They discovered that the essence of their peoplehood contains a special quality; and that special quality is G-d's Name that is associated with them.
Staying in Babylonia
We find in the Talmud [Shabbat 41a] a startling opinion regarding the nature of exile. When 4th-century scholar Rabbi Zeira wished to ascend to the Land of Israel, he needed to evade his teacher, Rav Yehuda. For Rav Yehuda taught that anyone leaving Babylonia for the Land of Israel transgresses the positive command, "They will be carried to Babylon, and there they shall stay, until the day that I remember them" [Jeremiah 27:22]. (Rabbi Zeira, however, disagreed with this interpretation. He held that the prophecy only referred to vessels of the holy Temple.)
Why did Rav Yehuda think that moving to the Land of Israel was so wrong?
Babylonia at that time was the center of Torah study. Great academies were established in Neharde'a, Sura and Pumbeditha. Jewish life in Babylonia was centered around the holiness of Torah. This great revival of Torah learning instilled a profound recognition of the true essence of the Jewish people. As such, Babylonia was the key to the redemption of Israel and their return to their land. Only when the Jewish people fully assimilate this lesson will the exile have fulfilled its purpose, and the Jewish people will be able to return to their land.
Rav Yehuda felt that individuals, even if they have already prepared themselves sufficiently for the holiness of the Land of Israel, should nonetheless remain in Babylonia. Why? The object of exile is not to correct the individual, but to correct the nation. The true significance of the Jewish people living in the Land of Israel - as an entire nation bearing the banner of the Rock of Israel - must not be blurred by the return of righteous individuals to the Land.
For Rav Yehuda, each individual Jew is like a Temple vessel. A vessel cannot fulfill its true purpose by itself, without the overall framework of a functioning Temple. So too, an individual can only join in the renascence of Israel in their Holy Land when the entire nation has been restored in its Land, via divine redemption.
PS: I am not arguing, Chas VeShalom , that we Jews should remain in Galut... I am just searching whether there may be any Talmudic argument for such a position...