According to 'History of the Viola' by M. Riley, the first printed editions (for cello) were in 1825 (Kistner), followed by an edition by Breitkopf und Hartel in 1826. There was also the Bach-Gesellschaft edition in 1879. Editions for the viola followed in the early twentieth century. These included one published in the US in 1916 by G. Schirmer (mentioned earlier).
A recent scholarly edition for viola (and probably the best edition available so far for the viola) is published by Peters (edited Rowland Jones No. 7489 ). It is based on original sources, has a preface with lots of information on playing the suites stylistically, provides the fifth suite in both Bach's original scordatura version and also a version for viola in normal tuning, provides the sixth suite in both Bach's original key of D and also transposed down to G (since the instrument for which Bach wrote this suite had an extra (E) string.
There is also the the Watson Forbes edition which was mentioned earlier.
Other editions include the Edition Reinhardt Munchen/Basel, Lifschey/Schirmer edition (1936) , International editon (edited Katims no. 3081), International editon (edited L. Davis no. 3064) , and United Music Publishers edition. I'm not sure when most of these were published as I don't have copies of them.
Edit: I found this
list of editions of the Bach cello suites but it only includes cello editions. l I don't know if it is of any use.
I also found another list of editions for viola:
International Music Co. 1982, c1980 edited by Milton Katims
Chester Music, c1951. transcribed by Watson Forbes. London
G. Schirmer, c1916 edited by Louis Svecenski. New York
G. Schirmer, c1944 edited by Louis Svecenski. New York
Verlag von Friedrich Hofmeister, [193-?] Suite 1-4 edited by Hermann Ritter. Leipzig
F. Hofmeister, [1965?] edited by Fritz Spindler. Leipzig:
Friedrich Hofmeister, [198-?], c1953 edited by Fritz Spindler
Alphonse Leduc, 1962 edited by Robert Boulay. Paris
The best place to find out a complete list of editions would be in the book 'Literatur fur Viola' by Franz Zeyringer