The reason for encouraging organ donation is to enable life-saving (and life-improving) transplants, but future technological breakthroughs might make this unnecessary. If scientists could produce artificial organs in labs, then we wouldn't need other people to donate their organs, since it would be possible to grow new organs to meet the demand.
This optimistic image may have come a step closer today, with the news that scientists have successfully grown a rat kidney. This is, however, only one step along a rather long road. The BBC article points to several unknowns, such as how long this artificial kidney will last. There's also the issue of cost: even if organs could be grown on-demand, if the technology is much more expensive than traditional transplants, then the latter are likely to continue. Finally, it seems that this particular mechanism requires an old organ in order to grow a new one, so this method will never avoid the need for donation in any case. That, I assume, is something that scientists will keep working on; in the meantime, donation is as useful as ever.