IMHO the future of eBay isn't stable - I'd consider it on "shaky ground". Here is my take as a seller in my 19th year.
Once J. Donahoe took over, the shift was "go big or go home". He was in full " Amazon Emulate" mode placing high volumes sellers such as your friend and brick / mortar stores significant priority over what he referred to as "The Noise". The Noise was the basic, honest, average seller.
Now that eBay is shifting back to the more mainstream seller, external factors are becoming a major issue. Shipping costs have skyrocketed. FedEx and UPS have switched to dimensional weight. The USPS has had a horrific rate increase to ship packages. So the average seller is getting boned hard. Meanwhile Amazon cuts massive deals with carriers, and the China sellers get fantastic subsidized shipping rates.
Today many sellers are selling their "good stuff" on Amazon, their "seconds / lower grade" products on eBay. Personally as someone who has be selling on eBay for 19 years now, I am trying to liquidate stock and am having a hard time doing so. I am honestly having a hard time moving product at below cost that once sold like mad. I say trying as I have items that just DO NOT SELL while I have competitors actually selling the very same product.
I personally am moving over to liquidation mode and letting eBay just be a hobby. The house is paid for, the car is paid for (I tend to keep cars for the long run, but they don't last forever) and I am exist on a modest traditional job. eBay will never be as relevant as it once was - they might just level off to being a small player of cheap goods and niche items on the cheap.