Kontakt 4 News from Native Instruments: Kontakt 4 is available for a limited period with a two hundred pound discount. The Kontakt 4 Crossgrade is a boxed retail version available for users of any sampler (hardware or software e.g. Structure). No proof is required - don't miss this promotion.
If you wanted to upgrade your very reasonably priced Kontakt 4 Crossgrade to Komplete 7 at some point in the future (or even today), just buy the Komplete 7 Upgrade - it's actually a bit cheaper than Komplete 7!