Workday (WDAY) and Veeva (VEEV) as great examples of just recently rallied SaaS stocks.
The true value of SaaS is just unfolding, not being stuck on old versions is just now sinking in. The above companies have customers go beyond the 5 year, sometimes 10 year mark - but they're not on some outdated version, figuring out how to patch that shit up. This is a revolution in enterprise that has not fully sunken in, there are still a lot of companies out there only dipping their toes into going SaaS.
Vertical clouds such as Veeva, as in going deep into one specific target industry, are a pretty good model to follow. Customer acquisition costs are super low, there is data out there to confirm this. All a reference sell, as CIOs talk to each other in a specific industry. Build a positive reputation, the sale follows. Product leads the way, not marketing.
The moat here being super deep industry expertise and data accumulation that gets harder and harder to compete with.
There will be something after SaaS, but it will take a while and it is utterly unclear what it will be.
Mainframes - Client/Server - SaaS - ??