Qlik Sense is designed to compliment QlikView. Sense allows users to explore their own data, whilst QlikView can be used to build “guided analytics”, meaning a designer will have defined a layout that provides pre-defined views of the data.
For developers there are some more powerful features in QlikView, but many of these have equivalents in Sense. If you have a business intelligence team providing analytics to the rest of your business, QlikView may be the best option. If you want to push more of the responsibility for creating visualisations on to the users who will be consuming the data then there is a lot of merit in using Sense.
With skills transferable between both platforms this doesn’t have to be a one-time decision and a blend of the two products is perfectly acceptable, as mentioned above.