I'm not sure he's right, though. All 3 Sony Readers are still listed on Borders.com, specs and all. They even have expected arrival dates (you can pre-order them). Surely the first step in dropping a device would be to remove it from the website?
It would appear to make a lot of sense, though. If Borders went with only Kobo devices, Mike thinks they could drop the tech support for the other devices. And even without Sony, Borders will still have the 2 Kobo ereaders as well as 4 tablets (2 from Velocity Micro and 2 from Next USA).
On the other hand, just because they don't carry the ereaders doesn't mean they won't have to support them. They've been selling Sony for what, 2 years now? That's a sizable number of customers they have to support. And all the stock answers to the usual problems are well established, so it's not like they will have to write them all over again.