Haleivi: I read the whole of Iggeret Teiman (in translation, of course) and I had to wait till the LAST paragraph in the letter to find what you are saying. The letter is very long and the rambam just has ONE paragraph concerning this oath (one oath only). He does say ( quoting shir hashirim 2-7 and 4-8) that we should not ‘awaken’ the “love”-meaning the redemption, early. However, it is abundantly clear from the whole iggeret that he means to say this only when someone declares himself to be the messiah (see letter) which ,of course, is scarcely the case nowadays with Eretz Yisroel.
Furthermore- the Rambam writes that this can only bring catastrophe and that the people will perish AFTER this has been done. For now, Eretz Yisroel remains a thriving place.
Lastly, nowhere in the “Jad” does the rambam mention these shevuos, suggesting that his words in the Iggeret were meant to discourage people from following pseudo-messiahs, not as an absolute injunction.