I recall something like this was reported a few months back, and you said you were reworking math alignment mechanisms at the time.  Now that you're getting ready for the Tex Live version, I want to bring attention to this issue once again, in the hope of getting it resolved.

Formula numbers are not placed at the far end when in RTL.  Here is a MWE:

\starttext

\input knuth

\placeformula
\startformula
E = mc^2.
\stopformula

\righttoleft

\placeformula
\startformula
E = mc^2.
\stopformula

\stoptext

Attached is the result from context version 2017.05.14 19:09.   Using \setupformula[location=left] gives similar results with directions swapped: output is as desired in LTR but slightly off the edge in RTL.

Thanks,

MHB