How does Presales work in a Customer Success world?

How does your company measure success?  Are subscription & renewal value seen as the most important revenue sources?  Over time these compound and outweigh the net new business from new customers. As a consequence, long term value starts to trump initial deal value.
Successful businesses with customers on renewal find that the initial sale value is less of a proportion of lifetime expected value.  Customers that renewal are also more likely to buy more products and expand the scope of their deployments.  Also new customers are less likely to buy subscriptions on products until they know they will use them. 
This means keeping happy customers is as important or more than winning new business.  As such, many companies start looking at customer success as an area to invest in directly, seeing the rise of a new organization, or that other parts of the company need to come together and support the way of ensuring customer success.
It also means we need to focus on setting realistic expectations of value, rather than getting business stakeholders over committed on what they should achieve

This means for a change of role for presales in customer success world
Obviously, we are still very much focused on winning new business, but we may have a secondary role in ensuring renewals, and helping cross-selling and upselling.  We may even want to start measuring the performance of presales in these activities.
Presales team members may be able to take part in realized value activities after the initial sale, including workshops, customer days, health checks and other regular or incremental interactions.  The catchphrase we are always in presales” becomes a reality - there is always the next sale with our customers to consider.
The initial sales team also need to avoid over-selling aspects of the solution.  Agree on gaps, areas of future improvement and correct false assumptions if they will impact customer success. In some companies, the customer success team may even have the right to reject or cancel new purchases if it will have a negative impact on customer success, due to the impossibility or difficulty in achieving the customer vision.

The rise of customer success also provides potential new opportunities and challenges.
First of all, customer success roles may have similar skills that many SEs have.  The chance to work closely over a long period of time with the same customers might be attractive to some SEs.  Seeing through the value realization with customers may also be an appealing option.
As such, a dedicated customer success division can offer career opportunities to SEs outside of the presales organization
Even without leaving presales though, SEs might have a bigger role than just supporting the new business sales team. They will have an ability to deliver value to more parts of the business, by working with other parts of the business on a planned or ad hoc basis.  This can increase the importance of the SE skill set in the success of the business itself.  

A customer success orientated world sees the long term value as more important than the initial win value of a customer opportunity.  Both are vital to a growing and successful business, but just winning new business cannot overcome a business with customer success and churn issues.  Ultimately the best business in a segment will be the one that can offer repeatable and loyal customers continual value.  The role for presales in a customer success orientated world is to ensure initial and continual value over the lifetime as a customer.