As a few others have mentioned, it takes time for prospects to turn into regulars or stars. Very rarely do guys come into the NHL and put up 80 points. The far more common route is a guy come up, plays 60ish games and has 30ish point. Next year more games and more points. 3rd year the same. That was the route with most of our stars now. It took them 3-5 years to hit their potential. So, are we a really good team in 3 or 4 years by standing pat? Maybe. First not all of our prospects will work out. Second Datsyuk is then gone. Third, will Z's back hold up? Fourth, will Franzen still be around or will concussions have ended his career by then?
Four years from now, Kronwall may also be done. same with Howard. E will be in his mid 30's. Most if not all of those guys will playing fewer games and putting up fewer points as they travel through their mid and late 30's. In other words, we will be treading water.
In 3 to 4 years, Datsyuk may be gone, but Z's back will be better than its been in a decade after his surgery, this type of procedure works wonder on the type of pain he's experiencing. Suggesting Franzen's career could be over due to concussions is as likely as suggesting Crosby's will, its a possibility but not one with great probability.
It is true though that all 3 will be a lot less productive than they are right now, but Nyquist, Tatar, Jurco and Sheahan will be at their peaks and in some of their cases will be far better players at that point than Ryan Kesler, especially considering Nyquist is already playing better than him.
What we need both now and for the future is a #1 defenceman, I think the chances of getting one out of Sproul, Ouellet, Marchenko, or Backman is greater than the chances of getting one via trade. The best we'll get right now is Edler who is another #2 guy. You have to draft and develop defensive anchors, once you have one you never trade it away.