The way I see it, there are four things "social" plugins/services for WordPress can do:
- Following: display links to allow users easily discover social accounts
- Sharing: display sharing buttons on individual posts for various social networks
- Auto-posting: publish new article links on social networks, optionally customizing the format for each one.
- Scheduling: facilitate publishing of older article links on social networks
I'd imagine it's pretty tough to upsell users on following and sharing. This is stuff that can be coded with a little bit of HTML and CSS.
But auto-posting and scheduling? That's more difficult, and I think you'd find customers more willing to pay for solutions that make those things easy.
I'd also research more niche social networks. A lot of social plugins offer zero support for anything outside of the most popular social networks (Facebook, Twitter, Pinterest, LinkedIn, Google+), including yours. That's fine for the vast majority of sites, but maybe there's a social network just for finance-related content that finance-related websites would love to see support for in sharing plugins, but can't find them.
Also, your exit intent popup feature is interesting. I wonder if that could be isolated in its own plugin, and then opened up to other things like email subscriptions, surveys, and the like.