Along with what's been said... realize that the KL5/6 bezels will be *substantially* larger than the KL4. The KL5/6 offerings are in a different ball game since they're meant for much larger, more expensive hosts. Since the current offerings of KLX products fit mechanically-switched lights, I wouldn't expect them to have adjustable brightness.
If by "better" you mean bigger, more expensive and capable of a tighter beam, then the KL5/6 should be WAY better than the L4. But if "better" means smaller, cheaper, and capable of a wider flood beam, you may be disappointed.
It certainly is exciting to see all these 5W offerings coming up in the near future!