In this article written in Hatzofeh in December/January 1947-8, a few months before the establishment of the State of Israel (and reprinted in Techumin volume 10 with new material added), Rav Zevin reviews the history of קדושת הארץ and possible ramifications of a renewal of significant Jewish settlement in the Land.
On one level, the Land has independent kedusha, as reflected in various statements in the Gemara and Midrashim about God's concern for the Land and how one who lives in Israel has a God, while one who lives outside of Israel is as if he has no God. This kedusha is eternal, and is not connected to where Jews are living at a given moment.
Rav Zevin then discusses the kedusha that accompanies Jewish settlement in the Land, and differentiates between the kedusha that came about at the time of Yehoshua's entry to the Land and that which devolved at the time of Ezra's leading the Jews back from the Babylonian exile. The kedusha from the time of Yehoshua was created via conquest and perhaps via the building of the Beit HaMikdash, and most commentaries hold that this kedusha was nullified when the first Beit HaMikdash was destroyed and the people were exiled.
By contrast, the Jews who returned to build the second Beit HaMikdash did not conquer the Land, but merely built up settlements, and thus the kedusha at that time was created via their seizing of the Land. However, there is a debate as to whether this kedusha was full-force, or whether it only created a d'Rabbanan-level obligation for מצוות התלויות בארץ such as giving תרומות ומעשרות. According to Rambam, the obligation was only d'Rabbanan, since we require ביאת כולכם - everyone coming to the Land in order to restore the full kedusha. As with the kedusha from the time of Yehoshua, there is a debate as to whether or not this second kedusha was nullfied when the Beit HaMikdash was destroyed.
Based on these considerations, Rav Zevin discusses several issues that may now become relevant as Jews were about to return after two thousand years to their Land:
1) The Negev - the southern part of Israel falls outside of the borders that were conquered by the Jews at the time of Yehoshua, but well within the area promised to the forefathers. As such, it is possible that while crops grown there may not be subject to an obligation to give תרומות ומעשרות דאורייתא, there may nevertheless be a fulfillment of מצות ישוב הארץ for one who lives there.
2) The overall kedusha of the Land - if those who returned from Babylon could put kedusha back into effect by settling the Land, is it possible that the same could happen with those who are now returning. And, if so, can they re-create the kedusha in a way that it could spread to regions that had not previously been settled?
3) If a majority of Jews return to the Land, will we reach a situation of ביאת כולכם that would make fulfilling the mitzvot of the Land into מצוות דאורייתא? This was debated by Rav Chaim Soloveitchik and his student Rav Isser Zalman Meltzer [interesting trivia - Rav Chaim's great granddaughter is Rabbanit Tova Lichtenstein and Rav Isser Zalman's granddaughter is Rabbanit Miriam Amital]. Rav Chaim held that ביאת כולכם was tied to a historical moment and could only happen during the days of Ezra, while Rav Isser Zalman felt that it could happen at any time. Beyond that debate, there is the question of whether ביאת כולכם means literally all Jews or if we could invoke the well-known dictum of רובו ככולו and only require a majority of world Jewry to move to Israel in order to have a higher level of kedusha kick in. Rav Zevin sides with the view that we can invoke רובו ככולו [ed. note - we are getting very close to this point right now].
4) The mitzva of settling the Land - Rav Zevin concludes by noting that according to Ramban, one of the 613 mitzvot is to settle the Land, which the Marcheshet rules includes living in the Land and acquiring land in Israel. As we now have our own State, we finally have, for the first time in two millenia, the opportunity to fulfill this mitzva in all of its aspects.
May we merit to see the continual flowering of the גאולה and may we do our part in helping Hashem to fulfill וקבצנו יחד מארבע כנפות הארץ.