This is certainly good for games and similar multimedia heavy type apps. However, if you're using C++ for portability for any sort of non-realtime needs you've lost your marbles, and would be better off with JavaScript (no, really) and/or platform specific code to leverage the class libraries of the respective platforms. C++ heavy apps on Android are larger, use more memory, and load less quickly. This isn't obvious…
Maybe if you're starting from absolutely nothing. If I had non-trivial functionality already written in native code then I suspect I'd rather write JNI bindings than do a complete rewrite in Java.
I'm also skeptical of 'use more memory' and 'load less quickly'. Even the GNU C++ standard library on an x86-64 desktop is a less than a megabyte. I can't imagine that being significant in either of those problem areas.