Samsung's stock-Android Galaxy S4 was announced at Google I/O and HTC's stock One was unveiled at the D11 conference, but apparently those two companies won't be the only ones to offer flagship phones without custom skins. AndroidGeeks has reported (with Android Central confirming) that the Sony Xperia Z will also be sold in the Google Play store in a "Google Edition," foregoing Sony's software customizations but maintaining identical hardware specs.
For now, rumors point to the "Google Edition" Xperia Z being available only in the US Google Play Store, with a possible announcement later this month. It's actually a little surprising to see Sony lag behind both Samsung and HTC in announcing a stock phone — the company has traditionally offered more support for "AOSP" stock ROMs on its handsets, especially with the Xperia S.
The "Google Edition" Xperia Z will reportedly be available "later in the year," so it's unclear (and perhaps unlikely) that it will be sold at the same time as Samsung and HTC's handsets, on June 26th. If the reports pan out and you factor in LG's Nexus 4, the top four Android manufacturers will all offer phones without software customization by year's end — an unprecedented situation in the Android ecosystem.