Give it about another 20 to 50 years. Until then, people will continue to call it experimental. One could say fiat money is experimental and is failing, but it lasted a hundred years. There are plenty of science experiments with people that have been going on for decades.
You could even argue capitalism is still an ongoing experiment 
Right now, it's not going too well in fact, with an ever increasing gap between poor and rich.
I don't know other open source software projects with as many talented devs, thorough security analysts and general global attention as Bitcoin and yet any other software project that comes near to Bitcoin in any of those aspects is long out of experimental stage. So I'd say Bitcoin is quite humble in still calling itself experimental
It has resisted a ton of attacks, you could even argue it's the software project that should be the most profitable to attack, yet it's still secure, still decentralized and still increasing in interest, adoption and price.
Experiment is going well so far!
