Two-stroke gas-powered lawn equipment is inevitably on the way out, because it exists at the confluence of two trends.
One is the increasing evidence about the unique environmental and public-health damage this obsolete equipment causes (as detailed in many previous entries on this site). The other is the rapid emergence of cleaner, quieter, more sustainable electric alternatives.
The driving factor in the second development has been the pace of research in improved battery technology. For general background on this field, please see an Atlantic article from 2014. And for the latest news, please see this announcement in the University of Texas newsletter about a breakthrough in battery technology from its labs.
From the announcement:
A team of engineers led by 94-year-old John Goodenough, professor in the Cockrell School of Engineering at The University of Texas at Austin and co-inventor of the lithium-ion battery, has developed the first all-solid-state battery cells that could lead to safer, faster-charging, longer-lasting rechargeable batteries...
The researchers demonstrated that their new battery cells have at least three times as much energy density as today’s lithium-ion batteries. A battery cell’s energy density gives an electric vehicle its driving range, so a higher energy density means that a car can drive more miles between charges. The UT Austin battery formulation also allows for a greater number of charging and discharging cycles, which equates to longer-lasting batteries, as well as a faster rate of recharge (minutes rather than hours).
As the Atlantic article explains, no one development will be "the" answer in battery technology. The significant point is the breadth and intensity of scientific, engineering, and commercial activity in developing more powerful, cheaper, longer-lasting batteries. This has obvious implications in hastening the advent of electric cars, and some aircraft -- and lawn equipment as well.
For more, please see articles in CleanTechnica, Digital Trends, Yahoo Finance, Mashable, and Fox News. The original scientific paper is here, in Energy and Environmental Science. And here is a video describing this latest breakthrough: