We haven't heard too much from Trent@MyGeekShow since he restructured his time late last year. He has however just uploaded a video outlining some exciting news.
These new professionally-built 4S packs are based on Panasonic's NCR18650GA Lithium-Ion cells which offer comparable energy density but with upwards of twice the power density as Panasonic's well known NCR18650B.
With the primary factor prohibiting use of Panasonic's NCR18650Bs in a broader range of unmanned aerial craft having been the relatively conservative power density (compatible only with the most efficient craft) as well as the limited availability of suitably sized and terminated packs, this new offering is a fantastic option for many smaller fixed-wing (AXN/Bixler/Wicked Wing XL) and mini-multirotor (<350 ships, not fpv racing) flyers who are chasing a bit of extra endurance.
The only problem I can see at this point is that they appear to be available exclusively via Amazon and shipping is not available to me here in the land down under. It is a shame too because I would love to grab half a dozen or so for my park flyer!