With the recent release of both PingPlotter 2.50 and MultiPing 1.01, we're actively moving forward and developing the Pro version next (although what nomenclature it will surface as is currently not entirely tied down, and neither are the features).
We're not really ready for "beta" testing at this point, and probably won't be for several more months. We'll post more information to our news page when we're ready to talk about this.
As for integration with Mozilla. My primary browser is Firefox, so we'll definitely evaluate that with any future browser integrations. Unfortunately, we've had to actively practice "scope management" to make sure we're releasing high-value high-quality products, and browser integration, although pretty high on the list, just isn't quite above the "cut" line yet. Hopefully, we'll get to this pretty soon.
Thanks for the feedback!