No it won't get updates anymore
Can you provide some source for your claim? At Build they said ALL Lumias (including 520, 620, 625, 720 - all with 512MB RAM) are getting the 8.1 update, and I don't see why they wouldn't get the next update as well.
I believe the person you quoted intended to have people panic about. All current WP8 devices will be getting the WP8.1 update, as well as the following GDR updates. No reason why they won't get the updates.
+625The brand new 630 which (I think) isn't even out yet, is have 512mb RAM, so... I don't think they release a phone without "future".