It is too soon to say that bacteria will not evolve to become resistant to this in the future. It is believed that teixobactin might have more protection against mutations in bacteria because it binds to fatty molecules (which are less likely to mutate than other proteins).
HOW IT MIGHT NOT BE A PROBLEM: Fortunately, the region teixobactin attacks in highly conserved in gram positive bacteria because it is structural.
They thought vancomycin was going to be the cure for antibiotic resistant bacteria, but overuse proved otherwise.
HOW IT MIGHT NOT BE A PROBLEM: Soil bacteria is starting to show some resistance from where they originally got it, so horizontal transfer is possible, but is very unlikely to pass to humans because of how infrequently information is passed from soil bacteria to those in humans.
It is not effective against gram-negative bacteria because it needs pepitoglycan.
HUMAN TRIALS
No human trials have been planned yet due to hesitation by many pharmaceutical companies to believe that this one will not confer resistance.
Hopefully within the next couple years as it progresses through preclinical trials. It was discovered very recently (January 2015), so as it continues to prove successful through preclinical trials and the semi-synthetic synthesis is proven trustworthy, we can expect to see a move towards clinical trials.
WHEN WILL IT BE AVAILABLE TO EVERYONE? Drug design and FDA approval is a long process. After the drug is designed, it will take up to 6 years for pre-clinical trials and another 6-7 years for clinical trials. With this timeframe in mind, teixobactin may be a commonly prescribed antibiotic within the next 10-15 years.