I'm still seeing them occasionally on auctions or of course ebay. Of course, often second hand.
I have an R-17 Grafitti set from early 2000s. It has been repaired twice in its lifetime, although one might have been my fault (not completely clear). I always worry about what happens if it fails, as my subway is point to point (out and back in MTH lingo), so if it fails, I don't have many great options (other than a plain old bump and go).
I guess my advice would be to get one now any way you can. If the electronics fail, I would guess it can be upgraded to PS3.
I did see new PCC trolleys at my local train shop (Ye Olde Train Shoppe in Boyertown, PA) with PS3. That would be a fall back plan, too, as these have the Trolley/Subway operation from MTH).
I wonder if Lionel will come out with an option now that MTH will be no more?