While I'm hopeful about geopolymers, I'm also rather wary about over-selling or minimizing the unknowns, instead of testing, testing and publishing test results.
I see a (potential, solvable) issue regarding what kinds of aggregate and reinforcing materials are long-term compatible with geopolymers. But IMHO, it can only be solved if somebody runs some real tests and publishes the results.
One issue that folks outside the concrete/structural engineering fields probably don't know about is the problem of alkali-aggregate reaction damaging concrete. See www.cement.org/for-concrete-books-learning/concrete-technology/durability/alkali-aggregate-reaction
The alkali-aggregate reaction is a real problem that occurs slowly, when some kinds of aggregates (e.g. gravel) are (mistakenly) used in cement/concrete/whatever-you-call-it, that causes the concrete to swell and crack -- sometimes leading to expensive failures. Note please that this can happen even in concrete containing no steel whatsoever!
Since geopolymers (at least the ones I've read about) add significant alkali chemicals to the mix, I think we need to be on guard against that extra alkali doing bad things to aggregate or other reinforcing materials.
IMHO, it's often issues like this (uncertainties about threats to long service life) that make builders, insurers and investors want to see real-world evidence that the latest tech wizardry won't bankrupt them.
I'm hopeful for geopolymers, but I've been fooled before by insufficiently-tested materials. So color me cautious.