yeah i dunno, maybe html5 or something else will become good (i haven't even looked at it so maybe it is) but what I really like is a good SDK. If you can be a lot more productive with a certain set of technologies, maybe it's more important than multiplatform.
writing native code also give more features. QML can't do 1/2 of what Nokia's normal Qt libraries do in c++ for example. Now imagine trying to use something else, you've just increased your problems again.
If you're going to spend your time learning something, choose wisely