The Rashash points out that it appears from the verses in Yechezkel 45 and 48 that when the Beis ha'Mikdash will be rebuilt bi'Meherah b'Yameinu, there will be a large gap between the city of Yerushalayim and the Beis ha'Mikdash of 14,750 Kanim (= 88,500 Amos, see Yechezkel 40:5), unlike today, that they border on each other. On the other hand, he notes, Rashi writes in Yechezkel 48:8 that Yerushalayim will be in the same location then as it is today.

By combining these two statements the Rashash infers that the Beis ha'Mikdash area, which presently borders on Yerushalayim, will not be in the place it presently is, but rather quite a distance away from its original place.

I assume that this is what you are referring to in your question. (I am not aware of who the "others" that you cited are, nor if their words are based on other sources.)

However, this much-cited Rashash is a poor source for such a novel interpretation of the verses; nor does it seem to be a correct interpretation of the intention of Rashi, as Da'as Sofrim in Yechezkel points out at length. I will try to summarize here his arguments against the Rashash's interpretation in brief, trying to avoid the more technical points:

(a) The Rashash seems to have misinterpreted Rashi's intention when Rashi writes that Yerushalayim will not be moved from its original location. Careful analysis shows that Rashi does not mean that Yerushalayim will not be moved as opposed to the Mikdash which will be moved.

Rather, Rashi is explaining why we find in Yechezkel that five tribes will have their portions south of Yerushalayim ( and the Mikdash), while today only Yehudah (and Shimon) inherited south of Yerushalayim. Rashi assures us that the discrepancy does not mean that Yerushalayim -- or the Mikdash -- will be moved from its present location. Rather, the portions of the Shevatim in the future will be much narrower strips, such that the five strips south of Yerushalayim will take up the same amount of land as the single portion of Yehudah did until then. Thus, Yerushalayim (and the Mikdash) will indeed be in the same general area.

If so, it may certainly be asserted that it is the Mikdash which will remain in the exact spot it is at present, while Yerushalyim proper will be located somewhat farther south.

(b) It is true that the verses in Yechezkel imply that the city is separated from the Mikdash, since after describing the location of the Mikdash the verses list broad swaths of land that were given to the Kohanim and to the Levi'im before describing where the actual city of Yerushalayim will be. This implies that the land of the Kohanim and the Leviyim separate Yerushalayim from the Mikdash.

However, it is possible to argue (albeit somewhat forcedly) that the verse is not listing the portions in order of their location. Rather, the verse is telling us to set aside portions for the Kohanim, the Leviyim, and the general populace (Yerushalayim) in the vicinity of the Mikdash. Their proximity to the Mikdash need not be based on the order of their listing in the verse. Thus, the areas of the Kohanim and Leviyim may be south of Yerushalayim, putting Yerushalayim itself alongside the Mikdash, as it is today.

(Note, however, that Rashi there 45:4-6 clearly seems not to have understood the verses in this manner.)

(c) The ABARBANEL (see Malbim as well) explains that indeed both Yerushalayim and the Mikdash will not be built in the same longitude and latitude as they are today. However, that does not mean that they will not be built in the same place as they are today.

The Navi tells us that Har ha'Zeisim will be split by an enormous earthquake when Mashi'ach comes. That earthquake will create the gap between the Mikdash and Yerushalayim by moving the very earth upon which they stand farther north and south respectively. Thus, even if the Mikdash will not be at the same latitude, it will stand on its original location, i.e. on the very earth and bedrock upon which the Akeidah took place.

I hope this clarifies the matter somewhat.

Best wishes,

Mordecai