You know just about everyone I know who rides wants a more powerful, bigger, better bike. It’s just the way it goes. One of my close friends has a Harley Street Bob. His is the 88ci motor (1450cc). I remember when he got it how impressed he was with the power, saying it was all he’d ever need. A few months into owning the bike he upgraded the pipes and added a power commander to get more power. Not to long after that a high performance intake for more power. The next season he had high performance cams installed for more power. Anyone seeing a theme here? Now he is talking about a big bore kit (I believe to a 1550). I’ve ridden this bike, it’s a great ride and IMO is insanely powerful the way it is now. Its the same way with people who buy sport bikes. There is no R type sport bike out there that can be used anywhere near it’s full potential on public roads, yet people upgrade them for more power all the time.
The point I’m trying to make here is that it doesn’t matter what bike you start with after getting familiar with it, 99% of riders want to upgrade. In most cases it’s not about needing a bigger, stronger, faster machine it’s simply wanting one. Unless you need the power for two up riding there is really no “need” for a bike more powerful than the S40. But that’s not going to stop you from wanting one.
Buy a bike that you are comfortable with now. But buy it knowing this, sooner or later (usually sooner) your going to want an upgrade. Everyone does. That’s the beauty of motorcycles, there’s ton’s of different styles out there and it’s great to try them all.