[Avodah] Since When Do Ashkenazim Daven Sephard?

[Micha Berger]

On Sun, Mar 11, 2012 at 11:17:49AM -0400, Prof. Levine wrote:
> The following is from an article titled "Reaching New Heights with  
> Siddur Avodas Hashem" that appears in the Hamodia Showcase Judaica  
> Supplement, Adar 5772.
...
>> Sephardic nusach with the kavanos of the Arizal. In the early years of 
>> the Chassidic movement, only the tzaddikim would daven Nusach Sephard,
>> while the chassidim, who lacked a profound understanding of Kabbalah,
>> would daven Nusach Ashkenaz. However, around the period of the Rebbe,
>> Harav Elimelech of Lizhensk, zy" a, (1717-1787), chassidim began  
>> davening together with their Rebbes- in the Rebbe's nusach...

I don't understand this portrayal that chassidus originally reserved
changing the nusach for only those who actually understood enough to
gain new kavanos, and only later the masses switch.

The Besh"t was niftar in 1760, during the lifetime of R' Elimelekh. Which
means what, that it took a couple to a few decades for the switch in
nusach to catch on? How fast do we expect a change of this magnitude
to occur?

Tir'u baTov!
-Micha