As far as "Cannon" goes, everything in 4e did happen, and the only "reversal" via 5e was that the Second Sundering reversed a lot of the physical changes that the Spellplague inflicted upon Faerun etc. As noted earlier, 4e moved the time-line forward about 100 years to DR 1479; 5e has moved the time-line forward only a few more years, so whatever History you can find from 4e, isn't far off the mark... For example, the 4e players guide has a little info, and the DM's campaign book has a lot more, about the whole of Faerun.
The "public beta" for 5e was set around DR 1482-1484, with the arrival of the "Chosen", the return of Bhaal, etc - see Madness in Baldur's Gate, Legacy of the Crystal Shard, Scourge of the Sword Coast, etc. PHB, SCAG, new published adventures for 5e etc are set from DR 1487+, the end of the Second Sundering. WoTC have deliberately focused mainly on the Sword Coast (like the original focused primarily on the Dales), and kept most things pretty vague, in order to try and avoid "cannon" cramping people's style. At least that's my interpretation.
On a personal level, I think it's a real shame that 4e advanced the timeline by 100 years, effectively wiping out most of the old source material's specific NPCs etc. But what's done is done...