I just think the software engineers that design these are barking up the wrong tree by believing that their simulations can ever fully model the sound of a tube. Every time I've had to use a modelling amp I've thought to myself ... ok, nice programmable EQ, but why not just put a tube in there?
It would save so much effort and expense and it would sound better. The best solution is the simplest.
The point however, is that eventually, they'll be every bit as good and in the long run much, much, much cheaper. The distance they've already come in a very short time is already incredible. I prefer valve amps at the moment, but I'm not going to kid myself that at some point no one on the planet will be able to hear the differences. Sure lots of people will still buy valve amps, but for the same reasons people still buy Rolexes; not because they keep the best time.
Nobody thought digital watches or cameras were any use once upon a time...