Just recently, a rumor surfaced that a Lumia 635 with 1 GB of RAM was coming soon. This has now been confirmed by an online German store Cyberport.de which has listed a 1 GB RAM version of the device for €139 ($159) which is interestingly just €10 more expensive than the original 512 MB version of the entry-level handset.
Unfortunately, the device does not have a front facing camera like the 512 MB RAM edition of the device but the RAM improvement makes it a decent upgrade indeed.
The rumor of this device first emerged when Norwegian carrier Telenor listed the device as '1 GB' RAM, however this report was rather inconclusive at that that and was believed to be a typo.
However, soon after, a new piece of evidence showed up which indicated that the listing by Telenor was not a typo after all. WindowsPhoneApps.es found numerous references to 1GB versions of the Lumia 635 for different carriers in the Navifirm Plus including Movistar and Vodafone in Spain:
Despite being listed, the 1GB Lumia 635 is unsurprisingly unavailable for sale on the German online store. It could be officially unveiled at the Mobile World Congress 2015 but your guess is as good as ours.