Recent talk has suggested that the popular Lumia 635 Windows Phone was in line for a popular hardware upgrade. One of the biggest limitations to the Lumia 635 (despite being one of the first Windows 10 preview phones) is the 512MB of RAM, meaning some apps just won't install. Various sightings of a 1GB version have started appearing across the web, but now it appears that the phone is somewhat official having been listed on Microsoft's own website.
The listing for the Lumia 635 on http://www.windowscentral.com/e?link=http%3A%2F%2Fclkde.tradedoubler.com%2Fclick%3Fp%3D259740%26a%3D2542549%26g%3D0%26epi%3DUUwpUdUnU29125%26url%3Dhttp%253A%252F%252Fwww.microsoft.com%252Fen-us%252F%26ourl%3Dhttp%253A%252F%252Fwww.microsoft.com%252Fen-us%252F&token=Z48_0fmB now lists 512MB or 1GB as the RAM for the phone, with a note that it's region dependant. Without mentioning which regions those may be. Considering the wide market the Lumia 635 has already launched in, it's not clear cut whether the new version could come in as a replacement, an alternative, or at all in places. Having 1GB of RAM seems to be the new baseline for Lumia Windows Phones, with the likes of the 435, 532 and 535 all recently launching with this amount.
We've reached out to Microsoft, with the statement "we have nothing to share" about all anyone is willing to say on the matter right now. With Mobile World Congress around the corner, perhaps it's in Barcelona where we'll learn more.