Acer has been one of those on again/off again OEMs in regards to Windows Phone 7. They have a very strong history with Microsoft, having released numerous Windows Mobile devices in the past and are one of their biggest OEMs for laptops and tablets.
We spoke with Acer's Dac Nguyen, Product Marketing Manger, Smart Handheld Business Group about Windows Phone and the prospects of Acer releasing some devices in the future. A few months ago, they spoke positively of the OS and there were even rumors that Acer had already been working on a phone.
From what we're told, Acer is still developing Windows Phone internally (they certainly didn't deny it), but as of yet have nothing to announce and seem still keen on Android (they released 11 Android phones in the last year). So like Asus, they're another OEM who is playing with the hardware and OS on an engineering level, but not officially developing any consumer product just yet. We suppose once Windows Phone gain more momentum, they'll be ready to commit and bring devices to market quickly, but until then they're sitting on the side lines.