You don't quite understand 401ks. You can choose either contribute tax free (traditional) or have tax-free growth (Roth). You can't do both in the same account.

This doesn't change the fact that the rules may be changed at some point, but given the ridiculously low limits on 401k contributions anyway you might as well put some money in one. Worst case scenario is you wind up paying taxes on t anyway, but then again you might not.

No matter how you slice it you won't wind up paying more taxes than you will if you pay them now and invest without any tax sheltering.