For CZ-UB to produce the 6.8 X 43mm then they would need a new mandrel to produce the barrels, reamers, go, no-go gauges. This would still be possible if demand was there but the ballistics for this round is'nt available yet, so you can imagine getting ammo(no ammo- no rifle sold). This round is a very specialised one: higher performance/low recoil are easily obtainable thru already existant rounds. This round is made as to carry maximum cariable quantity of ammo for a soldier to carry(remember .30-06, .308 getting replaced by .223/5.56mm).
The over-abondant surplus rifle are available(notice the armies are getting rid of odd calibers, poor performant calibers, crappy rifle design, etc.), which have given birth to new demand for: 7,62 X 39mm, .30-06, .308 ammo. This ammo has been made excessively cheap($/not quality vise) & giving access to a public eager to have a cheap($/but sometimes suffering in quality) rifle & ammo combo.
A much more easier access to low recoil/high performance is acquired with: 6.5 X 55mm(under-rated good performance), .243 Win., .270 Win.(another favorite), .308 Win., .30-06 Springfield, etc. If higher performance is needed then jump up to 7mm Rem. Mag. or .300 Win. Mag.
In a few years from now M-16 variants will abound the surplus market(making wonder why certain custom rifle-builders went with part kits), 5.56 will be floading the surplus ammo shelves. In 30 odd years from now the 6.8 X 43mm surplus will do the same. Don't fall to easily into the novelty act but invest in a good performance rifle.
Sincerely,
Fred