"Soon" is a term that has many meanings, the most notorious EVN meaning being the one used to describe ARPIA2's release date: it was first used by Peter "Pace" Craddock some time between May and August 2005, and finally took a definite meaning a few days before the plug-in was released (it was released on the 23rd of December 2006). The use of the word "Soon" to pinpoint such release dates is only second to the use of the expression "It'll be done when it's done".
"Soon" means "some time between now and later". On the Ambrosia boards, due to the infamous release of ARPIA2 (See above), it has been taken to mean "hopefully before EV4". TCs and large plugs are usually released "soon".
The most common causes of the "Soon" phenomenon is a loss of data on the plug maker's computer, which happened to the remnants of ATMOS (who made graphics for ARPIA2) sometime in 2005, delaying ARPIA 2 for another year, and massively underestimating the amount of work completing a large plug will require.