Water jet cutters and lasers can do some amazing things but I think the prospect that they could ever totally replace milling is practically zero. They supplement milling for operations where either their speed is a great advantage which is the case with laser in some instances, or their ability to cut very hard materials without introducing stresses or heat affected zones around the cut area as is the case for (abrasive) water jets.
Neither of these techniques can approach the precision possible with milling, they cannot do blind holes or slots and I cannot imagine how you would ever do a complex three dimensional shape with either of them.
About the only technology that could conceivably make end mills obsolete would be some form of EDM that was hundreds of times faster than current EDM and I think that is very unlikely.
An open mind is a virtue...so long as all the common sense has not leaked out.