Consider the QCD beta function. Its expansion in powers of the coupling is
where $a=\alpha/4\pi$. For simplicity let's neglect everything but the one loop term $\beta_0$. This term is given by
where $N_f$ is the number of fermion flavors. Notice that if the number of quark flavors is higher than $16$ the beta coefficient changes sign.
While performing the running of the coupling constant, when some energy thresholds are crossed we must increase the number of active fermions up to a total of 6. Now, for the fun of it, assume that more quark flavors are lurking in even higher energies. If this were to be true, and we reached a number higher than $16$, the sign of $\beta_0$ would change and the coupling would become large at high energies deconfining QCD. Is this picture right or I am I assuming something I shouldn't?