...I don't want to purchase the current outdated 30 inch Cinema display HD and I don't know how many years it's been sense the last update...
It's not like display technology has really leapt forwards over the past four or five years. 2560x1600 is still a lot of pixels, even if they've been selling them since the original Mac Pro. If Apple does release an LED backlit 30" it's not going to be a dramatic improvement over the old ones. It's unlikely a refresh is going to bring more pixels.
You can never have too many pixels or too much RAM.