I guess the first thing I would want to know is OP's definition of "relevant". If he means the best military cartridge,, then no, the 30-06 is probably not relevant. If he means will it kill deer, antelope, pigs, and similar animals, then yes, it is still relevant. Of course, there are always going to be both better and lesser cartridges for a specific purpose, so perhaps it would also be helpful if OP would let us know the purpose for which the cartridge will be used.
If all OP wants to know if the round still goes "bang" and generally kills stuff, then sure, it is relevant. If OP wants to know if it is the best cartridge for practical rifle, and 3 gun matches, it probably isn't as relevant as other rounds.
The 30-06 is a fine cartridge, and there are better, and lesser rounds. For general purposes it is a pretty good round.
As Jeff Cooper said:
"Ain't many problems
that a man can't fix,
with seven hundred dollars,
and a 30-06."