Depends on how the rules go but as it stands now why wouldn't they want to sell them. BMP have promiced a 3-year stability of regs, although Richard West hinted in a recent interview
that they might consider small changes depending on what the FIA do.
Assuming the regs don't change then with so many control parts there shouldn't be too much different in performance between a 2001 car and a 2002 car, unlike DTM where they've introduced a number of changes.
From a privateer team point of view a second hand BTCT car would make more sense than running a second hand SuperTourer a year or two ago.