Adult stem cells are what they came from. Stem cells from hair follicles can be teased to grow more hair follicles, thus curing male-pattern baldness. (I kid, of course.) Embryonic stem cells are differentiable. Under different conditions, they can be made to grow into lung tissue, or liver tissue, or nerve tissue, or brain tissue, or .... This is why they are so valuable and desirable for research. The "existing stem cell lines" were either not of sufficient differentiable quality to generate this level of diversity, or they were contaminated.
Again, what is missing is the starting material to make the leap forward. Looking at historical advances in medical science, it is conceivable that we will develop the ability to generate fully differentiable stem cells without resorting to the harvesting of human embryos (that admittedly would be discarded by fertility clinics, as they are today). It will just take 8 years longer than it could have.
__________________ Thefuture is fun,
The future is fair.
You may already have won!
You may already be there.
pac-man 
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