Barbara Beeton said (TUGboat vol. 34, pag. 4):
As noted on Don Knuth's TeX web pages,
he "intend[s] to check on purported bugs again
in the years 2013, 2020, 2028, 2037, etc."
So 2013 is the year for a debugging session.
After DEK has debugged (i.e. changed) TeX,
will there be identical changes in pdfTeX, XeTeX, and the other
engines according to the changes in TeX?